From Climate Central's Andrew Freedman:

Driven by a warmer-than-average June, the hottest ever July, and a warmer-than-average August, the summer of 2012 will go down in the history books as the third-warmest summer on record for the lower 48 states, the National Oceanic and Atmospheric Administration (NOAA) announced Monday. The nation’s second-warmest summer occurred just last year, and the only other summer that was warmer than the past two occurred during the Dust Bowl era of 1936. This summer was just two tenths of a degree cooler than the summer of 1936.

2012 warmest year

Temperature anomalies during the June through August period of 2012. Click on image for larger version. Credit: NOAA.

For the year-to-date, the U.S. had its warmest eight months of any year on record, and the past 12 months have been the warmest such period as well. During the eight-month period, 33 states were record warm and 12 states ranked in the top 10.

Sixteen states in the West, Plains, and Upper Midwest had summer temperatures among their 10 highest, as did seven Northeastern states from New Hampshire to Maryland. Colorado and Wyoming each had their record hottest summer. In Wyoming, the seasonal-average temperature was nearly 5°F above average.

The summer heatwaves this year were not quite as intense as the heat in 2011, but they affected more people. According to NOAA, more than 80 million people — about 10 million more than 2011 — experienced 100°F temperatures this summer. Climate change studies show that heat waves are becoming more common as manmade global warming continues. For the summer as a whole, warm-temperature records outnumbered cool-temperature records by a ratio of 3.5 to 1.

The extreme heat helped spread and intensify a massive drought that has shown no signs of abating in many areas, particularly across the West and High Plains. Nebraska and Wyoming saw their driest summers on record, and several other states in those regions saw one of their top 10 driest summers.

As of August 28, nearly 63 percent of the lower 48 states were experiencing moderate-to-exceptional drought conditions, and NOAA reported that the percentage of the nation experiencing the most intense drought doubled from 3 to 6 percent between July and August. The drought has led to a record wildfire season so far, with 3.6 million acres burned during August alone, mainly across the West. This was about twice the August average and the most for the month in the past 12 years. Interestingly, the number of fires was down this August, but the fires that did burn were larger than normal.

us third warmest summer

Acres burned per August wildfire since 2000. Click on image for larger version. Credit: NOAA.

The monthly average fire size reached more than 520 acres per fire during August, which was the highest for any August on record since such data began in 2000. Nearly half the acreage burned since January went up in smoke during August alone, and propelled the year-to-date acreage burned to more than 7.72 million acres.

Jake Crouch, a climate analyst at NOAA's National Climatic Data Center in Asheville, N.C., said cool water temperatures in the tropical Pacific Ocean associated with a La Niña event contributed to the hot and dry conditions in many areas this summer. “La Niña in spring kind of helped lay the groundwork for what was to come during the summer period,” Crouch said.

Crouch noted that the U.S. has had 15 straight months with above-average temperatures, which had never occurred since instrument records began in 1895. Also, summer was the third straight season to rank among the top five warmest, Crouch said, which also had never previously occurred. “All of this fits into the longer-term warming trend,” he said.

Records that go back to the beginning of the 20th century show that this year’s drought was exceeded only by events during the 1930s Dust Bowl era, as well as the major droughts of the 1950s.

Nationally though, the summer was only the 18th driest on record for the contiguous U.S., which reflected above-average rainfall across the West Coast, Gulf Coast, and New England. Florida, for example, had its wettest summer on record. Apalachicola, Fla., had 39.62 inches of rain, which was nearly 20 inches above average for the June-through-August period.

2012 us warmest year

Precipitation percentage of normal during summer 2012, showing the extent of the drought. Click on image for larger version. Credit: NOAA.

During August, the core of the heat and dryness shifted to the West after searing the Midwest and Plains states during June and July. Nevada tied August 1934 for its warmest August on record. Six additional Western states had a top 10 warmest August. The Northeast was also warmer than average during August.

Due to the drought and widespread temperature extremes, the U.S. Climate Extremes Index, which keeps tabs on the highest and lowest 10 percent of extremes in several weather and climate categories, was one and a half times its average value for the summer season.

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  • Brian Frendsen

    Brian Frandsen pours water over his head in an effort to cool off while building a cement block wall on Saturday, July 7, 2012 in Huntsville, Ala. (AP Photo/The Huntsville Times, Dave Dieter)

  • A dock extends into a dry cove at Morse Reservoir in Noblesville, Ind., Thursday, July 5, 2012. The reservoir is down 3.5 feet from normal levels. Oppressive heat is slamming the middle of the country with record temperatures that aren

  • Monique Miller

    U.S. Postal Service letter carrier Monique Miller drinks from a bottle of water as she delivers mail in the Feltonville section of Philadelphia on Saturday July 7, 2012. Temperatures of more than 100 degrees were forecast in Philadelphia and excessive heat warnings were issued for several states in the Midwest as a heat wave continued. (AP Photo/Joseph Kaczmarek)

  • A cow looks for something to eat as it grazes in a dry pasture southwest of Hays, Kansas in a July 6, 2012 photo. A new report shows the drought gripping the United States is the widest since 1956. The monthly State of the Climate drought report released Monday, July 16, 2012 by the National Climactic Data Center says 55 percent of the continental U.S. is in a moderate to extreme drought. That's the most since December 1956, when 58 percent of the country was covered by drought. (AP Photo/The Hays Daily News, Steven Hausler)

  • Steve Niedbalski shows his drought and heat stricken corn while chopping it down for feed Wednesday, July 11, 2012 in Nashville Ill. Farmers in parts of the Midwest are dealing with the worst drought in nearly 25 years. (AP Photo/Seth Perlman)

  • A marshal is treated for heat exhaustion on the 18th green during the first round of the U.S. Women's Open golf tournament, Thursday, July 5, 2012, in Kohler, Wis. Oppressive heat is slamming the middle of the country with record temperatures that aren

  • The gate is closed on a boat ramp leading to a dry cove at Morse Reservoir in Noblesville, Ind., Monday, July 16, 2012. The reservoir is down nearly 6 feet from normal levels and being lowered 1 foot every five days to provide water for Indianapolis. (AP Photo/Michael Conroy)

  • A sun bear reacts to triple-digit temperatures at the Henry Doorly Zoo in Omaha, Neb., Friday, July 6, 2012. The temperature reached 103 degrees Fahrenheit (39.5 Celsius) Friday. (AP Photo/Nati Harnik)

  • Perspiration collects on construction worker David Macmullen's face in the afternoon heat, Friday, July 6, 2012, in Philadelphia.

  • A sheep stands in front of a large fan in its pen at the All-American Junior Sheep Show at the Iowa state fairgrounds, Thursday, July 5, 2012, in Des Moines, Iowa. Oppressive heat is slamming the middle of the country with record temperatures that aren

  • Concrete worker Lenny Rose pours water over his head in an effort to cool off from the extreme high temperatures while building a commercial industrial park during a record breaking heat wave that is over most of the country, Thursday, July 5, 2012 in Springfield, Ill. (AP Photo/Seth Perlman)

  • Wyatt Young, 5, cools off in a fountain set up outside Busch Stadium before a baseball game between the St. Louis Cardinals and the Miami Marlins Friday, July 6, 2012, in St. Louis. (AP Photo/Jeff Roberson)

  • Boats sit in the bottom mud at the dock in the west cove at Morse Reservoir in Noblesville, Ind., Thursday, July 5, 2012. The reservoir is down 3.5 feet from normal levels. Oppressive heat is slamming the middle of the country with record temperatures that aren

  • Nia McCall, 8, plays on the "Sprayground" at Keeley Park in McLeansville, N.C. on Friday, June 29, 2012. A record-breaking heat wave swept across the southeast starting Friday and is expected to last through Sunday. (AP Photo/Burlington Times-News, Scott Muthersbaugh)

  • DROUGHT

    Farmer Joe Fischer holds ears of corn showing the variety of kernal development Thursday, July 12, 2012, at Fischer Farms Inc. in Owensboro, Ky. Normally the silks would already be brown, Fischer said. "There is no pollen left because the silks were delayed. . . because it has been too hot and dry," Fischer said. All five Owensboro-area counties have been designated primary disaster areas because of drought. (AP Photo/The Messenger-Inquirer, John Dunham)

  • The sun rises Sunday, July 15, 2012, in Pleasant Plains, Ill. Corn stalks are struggling in the heat and continuing drought that has overcome most of the country. All of Illinois is officially in a drought, and Illinois Gov. Pat Quinn plans a trip to southern Illinois to discuss the state's plans for responding to dry conditions. (AP Photo/Seth Perlman)

  • Arlington County residents pass the time in the Central Public Library after it was made an official cooling station in Arlington, Va., Saturday, June 30, 2012. Bob McDonnell declared a state of emergency Saturday after a powerful storm killed at least six people in the state and knocked out power for hundreds of thousands, leaving them without air-conditioning in the middle of a blistering heat wave.(AP Photo/Cliff Owen)

  • Lee Shinn wears one of the umbrella shade hats he sells to beat the heat at the corner of Jackson and Springdale in Memphis, Tenn., Friday, July 6, 2012. With temperatures again reaching the 100 degree mark, Shinns shady solution is a steal at three dollars a piece. (AP Photo/The Commercial Appeal, Brandon Dill)

  • Tanya Winters cools off in a fountain at Butler Park in Austin, Texas, on Tuesday June 26, 2012. Tuesday's high temperature of 109 was the highest ever recorded in June in Austin. (AP Photo/Austin American-Statesman, Jay Janner)

  • A the thermometer on the sign at Cincinnati Federal Savings and Loan on Glenway Avenue at Sunset Avenue on the East and West Price Hill line reads 101 degrees, in Cincinnati, Thursday June 28, 2012. Nate Mackey holds a towel and a cup of water as he crosses Sunset Avenue. (AP Photo/The Enquirer, Glenn Hartong)

  • In this Monday, July 2, 2012, photo, visitors to the Smoky Mountains float on the Little River in Townsend, Tenn. The National Weather Service has crunched some end-of-June numbers that give dimension to the heat wave. In Nashville, June continued the trend of above-normal temperatures for an eighth consecutive month. June went into the records averaging 1.3 degrees above normal, but most people will dwell on the last days of the month that set an all-time heat record for Nashville at 109 degrees on Friday. (AP Photo/The Knoxville News Sentinel, Michael Patrick)

  • John Rohlfing

    John Rohlfing, 38, wipes off his face as he works on his the construction of his new home Thursday, July 5, 2012, in North Aurora, Ill. He started at 6:00 a.m. and quit at 11:00 a.m. because of triple digit temperatures and the safety in those conditions. Oppressive heat is slamming the middle of the country with record temperatures that aren

  • In this July 11, 2012 photo, Steve Niedbalski chops down his drought and heat stricken corn for feed in Nashville, Ill. All of Illinois is officially in a drought, and Gov. Pat Quinn plans a trip to southern Illinois to discuss the state's plans for responding to dry conditions. (AP Photo/Seth Perlman)

  • Julie Rhoades, James Rhoades

    Julie and James Rhoades, of Brazoria, Texas, sit in the shade of their umbrella to avoid the hot sun as they watch a World Cup of Softball game in Oklahoma City, Friday, June 29, 2012. (AP Photo/Sue Ogrocki)

  • Aletta, a rough-legged hawk, flaps her wings as she gets a cooling shower from a hose at the Carolina Raptor Center in Charlotte, N.C., Friday, June 29, 2012. Temperatures were expected to exceed 100 degrees in the Charlotte area for the next several days. (AP Photo/Chuck Burton)

  • Children cool off from the intense heat at a waterfront park on Friday, June 29, 2012, in downtown Louisville, Ky. The city endured a second straight day of triple-digit temperatures as a heat wave settled in across Kentucky. (AP Photo/Bruce Schreiner)

  • Gail Ballinger gives a fan to Virginia Elliott and Lisa Elliott Wednesday at the Salvation Army Social Services office in Chattanooga, Tenn., Wednesday, June 27, 2012. Temperatures are expected to reach record levels by the weekend. (AP Photo/Chattanooga Times Free Press, Tim Barber)

  • Delores Smith loads a donated fan for her mother outside the Salvation Army Social Services building in Chattanooga, Tenn., Wednesday, June 27, 2012. Temperatures are expected to reach record levels by the weekend. (AP Photo/Chattanooga Times Free Press, Tim Barber)

  • A customer holds a blue bubblegum strawberry combo from Delta Snow, a shaved ice walkup business owned by 17-year-old James David Ingram, of Yazoo City, Miss., Wednesday, June 27, 2012. Ingram, who had applied for various jobs with no results, decided to start his own business and hopes the current heat wave will bring his new business a steady stream of customers. (AP Photo/Rogelio V. Solis)

  • Ruby Ellis, Margaret Gainey

    Ruby Ellis, 13, receives a shaved ice cup handed from Delta Snow co-owner Margaret Gainey, Wednesday, June 27, 2012, in Yazoo City, Miss. Gainey and her grandson James David Ingram, 17, own the small business and appreciate the fact their trailer has air conditioning for the hot summer ahead. They hope the current heat wave brings their new business a steady stream of hot customers. (AP Photo/Rogelio V. Solis)

  • The sun rises above the horizon Wednesday morning, June 27, 2012 in Decatur, Ala. as roofer Mike Murphy cuts out blisters in the roof of Decatur High School. Much of Alabama is gripped in an early summer heat wave that has already sent the temperature over 100 degrees in some Alabama cities. To cope with the extreme heat, Murphy's work day starts at 5 a.m. and ends at 1:30 p.m. (AP Photo/The Decatur Daily, John Godbey)

  • In this photo provided by Coby Baalman, cattle drink from a tank being filled with hauled water because the windmill and underground pump can't keep up with the volume being consumed at the Baalman ranch Wednesday, June 27, 2012, in Menlo, Kan. Across the country, more than 900 heat records have been broken in the past week. If the forecasts hold, an intense heat wave gripping the center and western portion of the country could mean more will fall. (AP Photo/Courtesy Coby Baalman)

  • In this photo provided by Coby Baalman, ranch hand Terry Moss walks through a parched corn field Wednesday, June 27, 2012, in wheat stubble that hasn't grown much in the dry heat in Menlo, Kan. Across the country, more than 900 heat records have been broken in the past week. If the forecasts hold, an intense heat wave gripping the center and western portion of the country could mean more will fall. (AP Photo/Courtesy Coby Baalman)

  • In this photo provided by Charlie Wilson, a herd of Red Angus cattle stay close to a watering hole at the Wilson ranch Wednesday, June 27, 2012, near Lakeside, Neb. Across the country, more than 900 heat records have been broken in the past week. If the forecasts hold, an intense heat wave gripping the center and western portion of the country could mean more will fall. (AP Photo/Courtesy Charlie Wilson)

  • In this photo provided by Charlie Wilson, a herd of Red Angus cattle stay close to a watering hole and the windmill at the Wilson ranch Wednesday, June 27, 2012, near Lakeside, Neb. Across the country, more than 900 heat records have been broken in the past week. If the forecasts hold, an intense heat wave gripping the center and western portion of the country could mean more will fall. (AP Photo/Courtesy Charlie Wilson)

  • Corey Tipton, 9, Andrew Koestler, 11, Alexandria Tipton, 5, Anna Koestler, 9, and Zachary Tipton, 7, lie in the shallows of the Riverwalk at the Mud Island River Park in Memphis, Tenn. Tuesday, June 26, 2012. (AP Photo/The Commercial Appeal, Jim Weber)

  • Robert Mitchell

    Robert Mitchell, a brick mason with Professional Masonry from Birmingham, Ala., cools off with some cold water while working at the Belk Hudson Lofts construction site in downtown Huntsville, Ala., Sunday, July 1, 2012. Huntsville, Florence and other parts of northwest Alabama are under an excessive heat warning with forecasters show high temperatures breaking 100 degrees across the state. (AP Photo/The Huntsville Times,Glenn Baeske)

  • Justin Pegram, 4, plays on the "Sprayground" at Keeley Park in McLeansville, N.C. on Friday, June 29, 2012. A record-breaking heat wave swept across the southeast starting Friday and is expected to last through Sunday. (AP Photo/Burlington Times-News, Scott Muthersbaugh)

  • Anne Blaauwgeers

    Netherlands' Anne Blaauwgeers, right, wears a towel on her head to ward off the hot sun as she cheers from the dugout during the fourth inning of a World Cup of Softball game against Puerto Rico in Oklahoma City, Friday, June 29, 2012. (AP Photo/Sue Ogrocki)

  • Tourist and criminologist Luisa Sanchez picks through rocks at the foot of the East River in Brooklyn Bridge Park during a days-long heat wave of above 90 degrees in New York, Thursday, July 5, 2012. (AP Photo/Kathy Willens)

  • Sophie

    Sophie, 3, from Connecticut, frolics with a water sprinkler set up at the National Mall near the Lincoln Memorial, rear, in Washington Saturday, July 7, 2012. The heat gripping much of the country is set to peak Saturday in many places, including some Northeast cities, where temperatures close to or surpassing 100 degrees are expected. (AP Photo/Manuel Balce Ceneta)

  • Summer Santa Claus Tom Osborn of Taylor, Pa. a member of the Greater Scranton Jaycees, cools his feet in a pool of ice at Lackawanna County Courthouse Square during First Night festivities held in downtown Scranton, Pennsylvania on Friday, July 6, 2012. (AP Photo/The Scranton Times-Tribune, Butch Comegys)

  • Avery Gass, 4, slips her way through streams of cooling water, Friday, July 6, 2012, at the Thorton Murphy Park splash pad in Spokane, Wash. (AP Photo/The Spokesman-Review, Dan Pelle)

  • Steve Milewski uses a net to remove dead Northern Pike in Dean Lake in Plainfield Township near Grand Rapids, Mich. on Monday, July 9, 2012. The recent heat wave is blamed for raising the lake water temperature higher than the fish can tolerate. (AP Photo/The Grand Rapids Press, Chris Clark)

  • Kevin Sanabria

    Kevin Sanabria, 10, plays in a small waterfall in Trenton, N.J., Saturday, July, 7, 2012. People were coping as temperatures in the region climbed into the high 90s. (AP Photo/Mel Evans)

  • Gabriel Salas

    Philadelphia firefighter Gabriel Salas, Engine 72, drinks a bottle of water after extinguishing a fire in an auto detailing shop in the Oxford Circle section of Philadelphia on Saturday, July 7, 2012. Temperatures of over 100 degrees Fahrenheit were forecast in Philadelphia and excessive heat warnings were issued for several states in the Midwest as a heat wave continued. (AP Photo/Joseph Kaczmarek)

  • Nia Bailey, Amari Swint

    Nia Bailey, 8, of Washington, left, and Amari Swint, 8, of Philadelphia, throw water balloons while in an inflatable pool during a seventh annual block party on Newton Street in northwest Washington, during record heat with temperatures in the triple digits, Saturday, July 7, 2012. (AP Photo/Jacquelyn Martin)

  • Tracy Canty

    Tracy Canty, of Washington, wears a towel over his head against the sun and heat while cleaning off a grill in Washington, during record heat with temperatures in the triple digits, Saturday, July 7, 2012. (AP Photo/Jacquelyn Martin)

  • Ryan Lankamp

    Gambler gets a cooling shower from Ryan Lankamp, left, of Shelbyville, Michigan, following competition in the Ranch Sorting Championship at State Fair Parkin Oklahoma City, Friday, July 6, 2012. (AP Photo/Sue Ogrocki)

  • Luis Saavevra shades from the heat with a giant U.S. flag umbrella as he plays chess on an over-sized board in Union Square as temperature reached the 90s on Friday, July 6, 2012 in New York. he National Weather Service reported late Thursday that the record-breaking heat that has baked the nation's midsection for several days was slowly moving into the mid-Atlantic states and Northeast. (AP Photo/Bebeto Matthews)

  • The sun rises Sunday, July 15, 2012, in Pleasant Plains, Ill. Corn stalks are struggling in the heat and continuing drought that has overcome most of the country. All of Illinois is officially in a drought, and Illinois Gov. Pat Quinn plans a trip to southern Illinois to discuss the state's plans for responding to dry conditions. (AP Photo/Seth Perlman)