July 11 1936 - Winnipeg's hottest day

On this date in 1936, Winnipeg registered its hottest day ever when the thermometer hit an unprecedented high of 42.2C (108F). In 136 years of weather records in the city (since 1872), Winnipeg has never recorded such an extreme temperature. The milestone was reached during a historic and unparalleled heat wave that gripped much of central and eastern North America that July. Many high temperature records in the US and Canada still stand from this historic heat wave.

Front page of the Winnipeg Evening Tribune, Monday July 13 1936
after Winnipeg's hottest and deadliest weekend on record

In Winnipeg, the heat wave started on July 5th and persisted for 2 weeks before easing on the 18th. From July 5-17, Winnipeg recorded 13 consecutive days above 30C, the longest such streak in Winnipeg history. During that stretch, 11 daily record highs were set or equalled which remain unbroken to this day.. an unparalleled feat in Winnipeg climate history. 9 of those days were 35C or more with 2 days hitting over 40C, including Winnipeg's all time mark of 42.2C on the 11th. The average daily high temperature during this period was an incredible 36.4C. Nighttime offered little relief from the heat with overnight lows rarely dropping below the 20C mark. In particular, the night of July 11-12th must have been unbearable for Winnipeg residents. After hitting an all time high of 42.2C on the 11th, the thermometer dropped to a "low" of only 28.3C the following morning, Winnipeg's warmest ever nighttime low and the only time on record that the daily minimum temperature has remained above 25C in Winnipeg. In fact, on that night the temperature was at or above 30C most of the night. Imagine living in those conditions without air conditioning! The heat was so unbearable, many residents were forced to sleep outside to escape the heat of non-airconditioned buildings. For many residents, the heat was too much with at least 70 heat related deaths recorded in southern MB, including at least 31 in Winnipeg alone along with another 40 hospitalized for heat prostration (as reported by Winnipeg Tribune). That death toll makes the 1936 heat wave the deadliest weather related event in Winnipeg history.

Reconstruction of hourly temperatures in Winnipeg on July 11 1936
Hourly temperatures are estimated based on 3 known values that day 

Even hotter temperatures occurred elsewhere in Southern Manitoba during the 1936 heat wave. Emerson MB near the US border recorded 13 consecutive days over 35C between July 5th and 17th, with an average high of an incredible 39.9C over the 13 day period. The heat wave included a phenomenal 7 days of 40C or more including a maximum of 44.4C on the 12th, Manitoba's hottest temperature on record. In fact, it was Canada's hottest ever temperature until Midale and Yellow Grass in southeast Saskatchewan hit 45.0C the following summer. During July 1936, Emerson registered 27 days of 30C or more, with an average high of 34.6C for the month, almost Arizona like. Between the 5th and the 13th, the town registered a remarkable 9 consecutive days of 100F or higher (37.8C) 

Daily temperatures at Winnipeg and Emerson
during the July 1936 heat wave

Further south in North Dakota, the town of Steele (between Bismarck and Jamestown) hit an unfathomable 49.4C (121F) on July 6th 1936 - the hottest temperature in North Dakota history. Such a temperature rivals the type of extreme heat found in the US desert southwest, and is almost as hot as Phoenix AZ's all time high of 50C/122F!  The weather observer in Steele (Mrs R.G. Armstrong) noted on her weather summary that "flowers on trees and shrubbery were cooked" due to the intense heat that day. July 6th 1936 saw all time highs established in Bismarck (45.6C/114F), Fargo (45.6C/114F) and Jamestown (47.8C/118F), records that still stand to this day. (read more about North Dakota heat here)

High temperatures (F) - North Dakota - July 6 1936

The hottest day in North Dakota history set all time highs

in Bismarck and Fargo (114F), as well as the state (Steele, 121F)

Official weather obs for Moorhead MN (near Fargo) for July 6 1936
The form notes an all time record high of 114F was set at 3:15 pm that afternoon

By all accounts, the 1936 heat wave was a historic and unparalleled heat wave that has yet to be matched in weather record keeping. 6 years of drought had left the Prairies bone dry and crops withered, allowing maximum heating of the surface during the hot summer months. For this particular heat wave, a huge upper ridge must have developed over central North America, allowing extreme temperatures to reach well north into southern Canada. The upper pattern would have been stationary for at least 2 weeks, allowing the unrelenting heat to persist for days on end, intensified by the early July sun. Whatever the cause, the conditions that led to the 1936 heat wave have never come together again to the extent they did 72 years ago this week. So as you complain about this year's cool summer weather, try to think what residents of Manitoba had to endure during the granddaddy of all heat waves - July 1936.

It was so hot during the 1936 heat wave, may residents were forced
to sleep outside. This scene was from St Paul Minnesota