Weather Almanac for July 2006

HOW HOT CAN IT GET?
THE GREAT HEAT WAVE OF 1936

The realities and experiences of the global warming we are currently experiencing remind some of us that extended periods of hot weather have visited North America sporadically in the past. The Dust Bowl Years of the 1930s are well known for drought and blowing dust, but they were also years of temperature extremes as well — both summer heat and winter cold. Of all the years in that decade, 1936 was most exceptional both for heat and cold.

During the winter of 1935-36, the US shivered through the second coldest winter ever across the nation. St. Louis, Missouri would go for 20 days without an above-zero ^oF (-18^oC) reading. In Minnesota the statewide average temperature between 22 and 26 January was -20.3^oF (-29^oC). The average temperature in the state of North Dakota never got above 0^oF for 18 consecutive days, and an all-time state record low of -60^oF (-51^oC) was recorded at Parshall on 16 February 1936. Devils Lake, North Dakota dropped below freezing on 27 November 1935, and did not rise above it until 1 March 1936, a period of 96 consecutive days. February brought record snowfalls. For the first time in memory, the Arkansas River froze near Little Rock.

Then in a complete flip, the summer became the hottest on record as a hot, humid airmass stagnated over the eastern half of the continent during July. The heat record for the summer may have been even greater except June in parts of the country such as Michigan was not exceptionally hot. The number of local temperature records set during the three-month period was likely as high as the heat. Even after seven decades, fifteen state maximum temperature records set during the Summer of 1936 still stand.

The Heat Is On

The heat began in the heartland in late June. Lincoln, Nebraska, for example, began a 35-day run of highs exceeding 90^oF (32^oC) on 24 June, peaking on July 25, at a record 115^oF (46.1^oC). That day's low was 91^oF (32.8^oC).

As July began, the heat spread north and west as a strong upper-level ridge locked itself over the central American Plains. On 5 July, Gann Valley, South Dakota hit 120^oF (48.9^oC). The next day (6 July), Steele, North Dakota reached 121^oF (49.4^oC), the hottest temperature ever recorded in the US outside its desert Southwest. It had been quite a year of temperature extremes at Steele. On 15 February, the thermometer had dipped to a bitter 60^oF below zero (-51.1^oC). That temperature swing within a calendar year of 182 F degrees (101.1 C degrees) would be unprecedented in US Weather annals.

The heat reached southeast Lower Michigan the next afternoon (7 July) when temperatures jumped above 90^oF (32.2^oC) and soared to 104.4^oF (40.2^oC) on the 8th. With afternoon relative humidity in the 30-40 percent range, the heat index over the next week pushed past 110 and reached 130. Night only brought brief and limited respite from the heat wave.

Prior to 1936, Detroit had experienced only seven days when the temperature reached 100^oF (37.8^oC) or higher in the 63-year history of official weather records. Yet the city would equal that total in one sweltering stretch from 8-14 July. The afternoon of Thursday 9 July, the mercury hit 102^oF (38.8^oC) causing the pavement on Livernois to buckle. The deformation raised a concrete hill four feet (1.2 m) high, halting all traffic at the intersection.

On 9 July, the baking temperatures had moved to the East Coast. At New York's Central Park Observatory, the mercury reached 106^oF (41.1^oC). The heat melted asphalt roadways and killed seven. Athletes competing in athletics for a berth on the American Olympic team collapsed and were rushed to nearby hospitals. The heat expanded the metal joints on all bridges over the East and Harlem rivers freezing them in the open position. Without the bridges, thousands of motorists on Manhattan Island were trapped.

The following afternoon, Phoenixville, Pennsylvania melted at 111^oF (43.9^oC) and Runyon, New Jersey roasted at 110^oF (43.3^oC), both state records which still stand. Further south, Martinsburg, West Virginia sweltered at 114^oF (45.6^oC).

In the era before air-conditioning, homes, businesses and stores held the oppressive heat of the day. Most people could only rely on fans and blocks of ice for some degree of cooling, but fans are little help and can be a hazard when temperatures rise above the mid-90s. Some could cool themselves in lakes, rivers and pools, and cities opened fire hydrants to provide cooling. Many slept outdoors.

Mid-month provided the national peak in summer heat. July 12 through 14 recorded the hottest three-day period in US history averaging 88.5^oF (31.4^oC) — the second warmest had occurred three days earlier — and temperature records fell like dominos. On 13 July, every weather station in the State of Wisconsin, save one which sat on a Lake Michigan island, exceeded 100^oF (37.8^oC).

Weather Map for 13 July 1936
Courtesy NOAA

July 14th was so hot in Iowa, that its 113 temperature-recording sites averaged 108.7^oF (42.6^oC). In the Midwest, Illinois and Missouri recorded temperatures of 118^oF (47.8^oC) for daily highs, Wisconsin and Minnesota hit 114^oF (45.6^oC); Michigan, 112^oF (44.4^oC).

August saw the center of heat slip southward over Oklahoma. Altus, Oklahoma's highs averaged 109.8^oF (43.2^oC) for the month, peaking at 120^oF (48.9^oC) for the second time that summer on 12 August — the same day as the Texas state record high was set. Ozark, Arkansas topped 100^oF (37.8^oC) for nearly three weeks, from 3 to 23 August.

Similar heat covered the nation from the Rockies to the East Coast. Fifteen states, all east of the Rockies recorded all-time highs that still stand. Only three states (Maine, Vermont and Rhode Island) did not have a high temperature in excess of 100^oF (37.8^oC). Eight state recorded highs of 120^oF (48.9^oC) or hotter.

The average daily maximum temperature for the month of July in Kennebec, South Dakota was 106.6^oF (41.4^oC) with a dozen days exceeding 110^oF (43.3^oC). Kansas City saw 100^oF (37.8^oC) or hotter temperatures on 53 days that summer; Lincoln, Nebraska had 41. Of the 88 Ohio weather stations, only three failed to reach the century temperature during July, and each of those fell one degree short.

Many locations also reported record strings of 100^oF or more. Lincoln had eleven straight days, Bismark, North Dakota and Chicago, eight; Detroit, seven. Clarendon, Texas was over 100^oF for all but two days between 12 July and 27 August.

Over the course of July and August, many cities set temperature records. Some of the more notable, Seymour, Texas melted at 120^oF (48.9^oC), the Texas state record which still stands. New York's Central Park hit 106^oF (41.1^oC) as did Duluth, Minnesota; Chicago's Midway Airport reached 104^oF (40^oC).

And while the bulk of the heat covered the continent east of the Rockies, Anchorage, Alaska had its own version of the heat wave: 43 days with maximum summer temperatures over 70^oF (21.1^oC), a mark still standing.

The heat waves of 1936 with its heat and high humidity frequently combining to give a heat index exceeding 120^oF (48.9^oC), and it killed more than 4,768 Americans. The records count 364 dead in Detroit, 570 dead in Michigan, the highest toll for any state.

Canada Too Hot

The heat wave, days with temperatures above 32^oC (90^oF), also spread into Canada during the first week of July, moving first northward across the central border into southern Saskatchewan, Manitoba and Northwestern Ontario, then spreading eastward into the Ottawa Valley. It began in southern Saskatchewan and Manitoba on 5 July, the hottest period there lasted thirteen days. In Ontario the heat wave lasted 8 days, beginning in the northwest on 7 July and ending across the full province on the 14th.

When the heat finally broke, 780 Canadians, most of whom were elderly and infants, had died from the heat. Another 400 or so were indirect casualties included several who drowned trying to escape the stifling heat. Ontario recorded the greatest number of heat deaths: nearly 600 persons of which 225 died in Toronto. Manitoba's heat-related death toll exceeded 70. By comparison, the previous summer had registered only 42 heat-related deaths. High humidity added to the discomfort and the deadliness of the heat wave.

Crops withered under the heat and dryness, and wildfires consumed vast tracts of tinder-dry bush in Ontario and the Prairies. Many fruit withered on the trees and crops wilted. The hot weather caused wheat crop losses estimated at $514 million (1989 US dollars). The heat buckled sidewalks and highways and softened asphalt as ground surface temperatures soared to unimaginable levels. According to David Phillips of Environment Canada, surface temperatures exceeding 65^oC (149^oF) were measured. Railroad tracks and bridge girders twisted in the heat.

The hottest day occurred in Manitoba. St Albans registered 44.4^oC (111^oF) on 11 July, and Emerson equalled that mark the following day. These readings still stand as the hottest on record in that province. In Winnipeg, temperatures exceeded 32^oC (90^oF) for 13 consecutive days, peaking at 42.2^oC (108^oF) on the 11th, the hottest day on record for that city. That night the minimum temperature recorded was 28.3^oC (83^oF). In Northwestern Ontario at the town of Atikokan, the hottest day (11 July) reached 42.2^oC (108^oF) which tied a provincial record set in 1919. Two days later, the mercury soared in Fort Frances to a level which again tied the Ontario heat record. Heat in the eastern region of Ontario did not quite reach that in the west, but it was still stifling, the hottest period ever observed in that part of Canada where weather records extended back nearly a century. Toronto peaked on 10 July at 41.1^oC (106^oF). The mercury only fell to 26.6^oC (80^oF) during the following night, setting a new record for highest minimum temperature.

Eastern Canada never reached those extremes of temperature, the record highs for the Maritime Provinces had been set the previous summer in mid-August. However, Newfoundland would see three straight days over 32^oC (90^oF) in early August, the longest string of such temperatures in provincial history. Saskatchewan would reach record temperature levels, but the highest to ever be recorded there would occur in the following summer.

Dust Storms Fly

Three quarters of the US was extremely short of rain, and the heat produced extreme drought conditions. Ludlow, South Dakota had just 2.89 inches (73.4mm) of precipitation that year. Eastern Nebraska saw only 8 percent of its average precipitation total for July, and Iowa only 14 percent of the normal. In Oklahoma, the state-averaged precipitation for August was only 7 percent of expected.

During the summer of 1936, the number of dust storms across the central Great Plains increased to 68 (only 1937 with 72 experience more), and at least four major dust storms swept across the nation.

"Fleeing a dust storm" Cimmaron County, Oklahoma
Arthur Rothstein, photographer, April, 1936 (Library of Congress)

Final Words: An Update

Addendum: August 2006

Seventy years later, temperatures across the United States soared during July. Extreme heat was reported just about everywhere. But hot as it was, the average temperature for the US (in the 48 contiguous states) of 77.2^oF (25.1^oC) in July fell just shy of the record of 77.5^oF (25.3^oC) set in July 1936, according to the National Climatic Data Center. July's heat set over 2,300 daily high temperature records across the nation, mostly in the Midwest and West. An additional 3,200 records fell for the warmest nighttime temperatures.

The most pronounced heat wave affected much of the nation from 16-25 July reaching from the Pacific to Atlantic shores. The hottest official temperature, outside the SW desert was 120^oF (48.9^oC) at Kelly Ranch/Usta, South Dakota. Montana was also baking, major reporting stations showed 20-23 day with temperatures above 90^oF (32.2^oC). Among the many notable heat events in the month are:

15 July 2006, Pierre, South Dakota: Pierre sets its new all-time daily maximum temperature record: 117°F (47.2°C).

16 July 2006, Valentine, Nebraska: Mercurt soars to daily maximum temperature of 113°F (45°C).

21 July 2006, Western Washington: An unusual heat wave in western Washington breaks five maximum temperature records: Vancouver at 104°F (40°C); Olympia at 100°F (37.8°C); Seattle at 97°F (36.1°C); and Hoquiam at 90°F (32.2°C).

21 July 2006, San Francisco, California: San Francisco International Airport's high of 83°F (28.3°C) broke a 52-year-old record of 80°F (26.7°C).

22 July 2006, Palm Springs, California: Mercury soars to 121°F (49.4°C).

26 July 2006, Death Valley National Park, California: The low temperature for the day bottoms out at a scorching 104°F (40°C). The day's high was only 116°F (46.7°C).

Addendum: September 2006

Like the hot month of July, the Summer of 2006, defined as June 1 to Aug. 31 by the National Climatic Data Center, the continental US had an average temperature of 74.5°F (23.6°C). According to the NCDC's Climate Monitoring Branch, this ranks as the second warmest for the nation since 1895, when such records were begun. The warmest US summer on record was the Summer of 1936 with an average of 74.7°F (23.7°C).

Of the US's ten hottest summers, five came during the decade of the 1930s and four, so far, in this opening decade of the 21st Century. The other hot summer came in 1988, and extreme El Niño year.

Learn More From These Relevant Books
Chosen by The Weather Doctor

• Burt, Christopher C.: Extreme Weather: A Guide and Record Book, 2004 (pb), W. W. Norton & Company, ISBN 039333015X.
• Williams, Jack: The Weather Book, 1997, Vintage Books, ISBN 0-679-77665-6.

Written by
Keith C. Heidorn, PhD, THE WEATHER DOCTOR,
May 1, 2006, Updated 15 August and 14 September 2006.

The Weather Doctor's Weather Almanac How Hot Can It Get? The Great Heat Wave of 1936
©2006, Keith C. Heidorn, PhD. All Rights Reserved.
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