August Continues Winnipeg’s Heat Streak

August closed out with another 30°C+ day, rounding out what ended up being another above-seasonal month, continuing Winnipeg’s above normal temperature streak to 14 consecutive months.

August 2012 Summary

2012 Departure from Normal Temperature, with Year-to-Date mean

2012 departure from normal (or monthly anomaly of) temperature. The year-to-date mean is also plotted.

August 2012 closed out with an average temperature of 19.2°C, 0.51°C above the normal of 18.7°C. At +0.51°C above normal, the month of August ended as the closest-to-normal month so far this year; the next closest was May which ended at 0.8°C above normal. The warmest day in August 2012 occurred on August 29th, where the mercury soared to 35.4°C, just shy of that day’s record of 36.1°C set in 1972. No new daily record high temperatures were set this August. The coldest night this August was on the night of August 18/19th where the temperature dipped all the way down to a chilly 4.5°C. This was well above August’s record low temperature of –1.1°C set in 1888. New new daily record low temperatures were set this August.

2012 Departure from Normal Precipitation, with Year-to-Date total

2012 departure from normal (or monthly anomaly of) precipitation. The year-to-date total is also plotted.

August ended with a significant deficit of precipitation compared to normal. Usually we see close to 80mm[1] of precipitation, however this month we saw just 44mm. This continues the Winnipeg’s precipitation deficit to 3 consecutive months.

In other miscellaneous August statistics:

  • We finished the month with 6 days at or above 30°C.
  • August 2012 ended up as only the 45th warmest August on record.
  • The greatest precipitation event this august was 23mm on August 4.
  • This month’s precipitation accumulation of 44mm pales in comparison to the record wettest August that occurred in 1985, where Winnipeg received a whopping 218mm of rain.
  • We quadrupled the record driest August’s (1915) total precipitation amount of 10mm.

2012 So Far

As mentioned before, August’s deviation from normal temperature of 0.51°C has continued the above normal trend for 2012. Every single month this year has been above normal temperature-wise and August marks the 14th consecutive month of such weather.

September 1st marks the start of meteorological fall, so we can take a quick look at Summer[2] 2012. Temperature-wise, we ended up as the 14th warmest summer, although it was an extremely close race…

Top 15 Warmest Summers on Record
Year Average Summer
1 1988 21.0°C
2 1983 20.6°C
3 1961 20.4°C
4 1955 20.2°C
5/6 1930 20.1°C
5/6 1963 20.1°C
7/8 1933 19.9°C
7/8 1995 19.9°C
9 1991 19.87°C
10/11/12 1919 19.83°C
10/11/12 1921 19.83°C
10/11/12 2006 19.83°C
13 1936 19.767°C
14 2012 19.761°C
15 1932 19.7°C

If you round to tenths, then there is a 5-way tie for 10th place, however looking closer, we can see the finer details and sort things out.

Year-to-Date Temperature Anomalies for Winnipeg, MB

Year-to-date temperature anomaly, by month, for 2012 (red) compared to the other 139 years on record for Winnipeg, MB, with the five warmest years (orange) and five coldest years (blue) noted.

Looking again at our Winnipeg temperature anomaly climatology, we’ve added in August of this year, and we can now see that we are the most above normal that we’ve ever been. While we were chasing 1987 last month, with August’s +0.51°C temperature anomaly we’re now 0.25°C above 1987’s August YTD anomaly. At this point, it’s pretty much guaranteed that 2012 will end upon the top 5 hottest years on record, it’s just a matter of where exactly we end up.

June, July and August all had below-normal amounts of precipitation which has left us with a 118mm deficit for the summer months. Typical summer rainfall is 247.5mm, which puts this summer at only 52% the normal amount of precipitation. This is a troubling trend; 2011 placed as the 5th driest summer on record, and 2012 managed to sneak into the top 10:

Top 10 Driest Summers on Record
Year Summer Rainfall
1 1929 76.7mm
2 1886 77.2mm
3 1961 91.0mm
4 2006 91.5mm
5 2011 93.0mm
5 1889 96.0mm
7 1894 97.1mm
8 1915 114.8mm
9 1936 121.4mm
10 2012 129.5mm

Due to our wet spring, however, we’re “only” 67mm below our normal precipitation amounts on the year so far.

The Rest of 2012

While seasonal forecast have very little skill, there are a few things that can give us an idea of how the rest of the year is going to shape up. With Arctic sea ice at a record low, it will take longer than normal to establish a pool of cold Arctic air. In particular, the delayed onset of ice over Hudson Bay can inhibit the development of a true Arctic vortex over the area. This feature sets up a strong NW flow over the NWT and eastern Prairies and is often responsible for the advection of Arctic air southwards into the Prairies and Northern Plains. The inhibition or absence of this feature means that, while cold outbreaks can never be ruled out, it’ll be much more difficult for the cold air to actually stick around.

Another feature to keep an eye on is El Niño, the feature responsible for bringing warmer waters to the eastern equatorial Pacific. When El Niño is weak, it’s effects can be limited to areas further west in the Prairies[3], however in moderate-to-strong El Niño events, Southern Manitoba will often see warmer-than-normal winters. In weak-to-moderate events, precipitation can be increased over the region as the storm track cuts through the area, but in stronger events, the storm track is often to our north and Winnipeg enjoys relatively warm, dry winters in a bit of a no-man’s-land in the middle of a strong split upper flow.

That being said, it’s quite likely that the onset of winter will be delayed due to the delay in development of a pool of cold Arctic air, and it’s all but guaranteed that 2012 will go down as one of Winnipeg’s warmest years on record.

  1. August’s 1981–2010 normal precipitation amount is 79.4mm.  ↩
  2. Meteorological summer runs through June, July and August.  ↩
  3. British Columbia and Alberta, mainly. Saskatchewan marginally.  ↩


Brad lives in Winnipeg with his wife and two children and is the founder of A Weather Moment. He has loved weather from a very young age and has followed that passion through his life so far. He received a B.Sc. in Earth Sciences with Specialization in Atmospheric Sciences and is currently employed in the field of meteorology. You can find the author as WeatherInThePeg on Mastodon.

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