Friday, July 11, 2008

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


  1. Do long range forecasts suggest any summer-like temperatures in the future for southern Manitoba. Today truly feels like a October day...

  2. Doesn't get much worse than today for a mid July day in southern MB. Feel sorry for those at the Folk Festival.. today's weather would have tested the patience of even the most diehard fan! As for prospects of more summerlike weather... looks better tomorrow and Monday, but then unsettled at times this week with no big warmups forecast. Models hinting at warmer temperatures next week, but at this point, I'll believe it when I see it. Seems like the jet stream does not want to migrate north of us this year..

  3. Thanks. That historical bit on our hottest day was very interesting. I remember the summer of 1961 in Saskatchewan and it sounds very much like that. I'm sure it wasn't as hot in 1961, but it was relentless.

  4. I wonder if we'll ever be able to beat that 1936 record. The airmass must have been very dry to reach such an extreme temperature.. it's much more difficult to hit those high temperatures when there's a lot of humidity around. I suspect dewpoints in the 1936 event must have been unusually low for mid July.. perhaps 10c or lower. 6 years of drought and little or no crop growth would have contributed to little surface moisture available in the atmosphere. Combine that with a strong early July sun angle, a massive upper ridge with 850 temperatures likely close to 30C, and a southwest flow, and you have all the ingredients to hit 40C+ temperatures over southern MB. Nowadays, we have better farming practices and irrigation techniques to help minimize such a widespread crop failure as in the Dirty 30s. That, plus the fact that we seem to have wetter summers now, help add additional surface moisture that makes it that much more difficult to hit those extreme temperatures. Winnipeg has hit 40C or more on only 3 occasions since 1872.. twice during the 1936 heat wave (41.1C and 42.2C), and once on Aug 7 1949 (40.6C). We haven't hit 40C in almost 60 years now.

    But it's still possible.. in early June 1988, we had a similar setup to the 1936 event that gave 40C+ temperatures over much of southern SK. Time will tell if such an event will happen again over southern MB.

  5. Unbelievable temperatures! At that times it must've been really unbearabable for the people who had to suffer trough such a long and hard heat wave without AC as you mentioned...

    Seriously, I never thought the Canadian Prairies could reach those incredible temperatures! 45C!!! Here in Europe the summer of 2003 was probably something similar, with lots of records broken.

    I remember the hottest day here we hit an unprecedent 43.6C and I hope I'll never have to suffer it again!!! Next night the "minimum" temperature was 29.6C, also a record. I couldn't sleep for several days... But at least I could go to the malls or drive my car with the AC on! Those people in the thirties, well, poor them...

    By the way, congratulations for your site Rob!

  6. Thanks for that bit of history Rob.. very interesting. Yeah since the 80's especially, topsoil moisture has remained too high for a widespread heatwave pattern to emerge.. too much energy going into evapotranspiration giving us cooler temps but increasing the moisture content in the boundary layer.

  7. Hi Mikel..

    How's the summer this year in Spain? Not much of a summer here this year.. still waiting for some heat!

  8. Hi Rob!

    Not much of a summer in Northern Spain either... most of the days are cool, cloudy and stormy with max in the low 20s. At least some nice tstorms going on!

    I've seen you've been below normal for many months in a row... hope you finally get some deserved heat!!! How is the tstorms-tornadoes season going in Manitoba? I still remember the mighty tornadoes you had last summer!

  9. We've had 8 tornadoes so far in southern MB.. all of them weak (FO/F1). Nothing like the violent tornadoes we had last year thanks to more heat and humidity. This year we have the dynamics for storms to develop, but heat and humidity have been lacking to fuel the big supercells. Things could change though if we get some heat!

  10. Well, even if they are weak, 8 tornadoes so far sounds incredible to me! I've read in other post that you haven't reached 30C yet... not very summerlike, that's for sure!

    Here we're waiting for real summer to come too, especially after a very wet and cool spring. Let's hope we all enjoy a bit of nice warm weather!!!

  11. Better give your info to the Free Press. The other day they said the hottest ever in July was 37. 8 on July 12, 1939. For some reason Environment Canada's website gives no stats before 1938.

  12. ann.. That's because they're only using data from the Winnipeg airport which started records in March 1938. Prior to that, weather statistics for Winnipeg were taken at St John's College (downtown) from 1872-1938. These are also considered official statistics, and are part of Winnipeg's official climate record.

  13. Excellent piece! I have often wondered about July 1936 as its daily records never seem to be beaten. That this heatwave occurred during Depression/drought conditions is even harder to imagine.