Category
|
Sep 2017
|
1981-2010 normal
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Deviation
|
Rank
|
Avg high temp.
|
20.1°C
|
19.1°C
|
+ 1.0°C
|
39th warmest (tie)
|
Avg mean temp.
|
14.2°C
|
12.9°C
|
+ 1.3°C
|
23rd warmest (tie)
|
Avg low temp.
|
8.2°C
|
6.6°C
|
+1.6°C
|
18th warmest (tie)
|
|
|
|
|
|
Total rainfall
|
67.3 mm
|
47.4 mm
|
+ 19.9 mm (+30%)
|
41st rainiest
|
|
|
|
|
|
Avg dewpoint
|
8.1°C
|
7.5°C
|
+ 0.6°C
|
18th highest (tie)
|
|
|
|
|
|
T-storm days
|
2 days
|
3 days
|
- 1 day
|
Equal to median
|
|
|
|
|
|
30°C days
|
1 day
|
1 day
|
Normal
|
31st most (tie)
|
|
|
|
|
|
Avg sustained wind
|
18.9 km/h
|
16.9 km/h
|
+ 2.0 km/h
|
13th windiest (tie)
|
|
|
|
|
|
First Freeze Date
|
Sep 29
|
Sep 23
|
6 days late
|
20th latest (tie)
|
|
|
|
|
|
All stats and rankings in the table are from data going back to 1872, except: dewpoint, t-storm days and average sustained wind which are from data going back to 1953.
- Record maximum 34.8°C on September 12. Old record 33.3°C in 1952. Also 2nd latest date to reach 34°C (latest was Sep 27, 1952). Also hottest day of the year, beating 34.5°C on June 2. This was the second latest hottest day of a year since 1872 (latest was Sep 19, 2004).
The main story in terms of warmth this September was actually the daily lows, rather than the daily highs. The lows averaged 8.2°C, 1.6°C above normal and tied for 18th warmest. The first frost wasn't until September 29 at Winnipeg Airport, 6 days later than normal and tied for 20th latest first frost date since 1872. Most parts of the city did not fall below freezing however. There was some frost reported on roofs and open fields despite above-zero temperatures at station levels. Sub-zero temperatures occurred close to the surface in spots as a result.
The hottest day of the month (and the year) was on September 12 with a high of 34.8°C. This date saw widespread records being obliterated across southern Manitoba. Using a MB AG/ECCC merged dataset and locations with at least 30 years of records, 37 of 54 stations across southern Manitoba broke a heat record on September 12. The highest temperatures were in the Red River Valley which benefited from its lower elevation, from the downsloping southwesterly winds down the escarpment and from the fact that smoke did not move in until late afternoon or early evening. The hotspot was Carman with an incredible high of 36.0°C, breaking its old record of 30.6°C in 1908. Starbuck and Elm Creek also exceeded 35°C with highs of 35.6°C and 35.4°C respectively. The map below shows the 37 heat records that were broken across southern Manitoba. A swath of southwestern Manitoba did not break its record because of cloud and smoke which moved in earlier in the afternoon:
East of the Red River Valley, an early frost occurred on September 6. Steinbach recorded a low of -1.3°C, the 5th earliest first fall freeze on record since 1956. This was about 1.5 to 2 weeks earlier than normal.
Two thunderstorm events occurred in Winnipeg. On September 4, small pea sized hail (2-5 mm diameter) fell in parts of the city. On September 22, intense and at times frequent lightning brought a good light show to the city. Heavy downpours also brought beneficial rains. 25.2 mm fell at the Airport, the rainiest day of the year. If this holds through the rest of the year, this would be the 10th lowest maximum daily rainfall in a year since 1872. The storms also dropped large hail west of the city with hail as large as toonies or golf balls near Rathwell.
Strong storms also occurred on September 19. Wind damage was reported near Wawanesa (no wind measurements available however). Flooding rains also fell as a result of training storms. 97 mm of rain fell in Baldur and 67 mm fell in Boissevain. in both these communities, these were the highest daily rainfall amounts on record for September. In Baldur, the 97 mm daily rainfall amount in itself was enough to rank this September as the rainiest on record, beating 95.4 mm in 1977 (records since 1962). The 97 mm daily rainfall also broke the old daily rainfall record for September of 47.0 mm on September 10, 2003. Further east, 53.7 mm of rain fell in 1 hour in Elm Creek. Lastly, a 104 km/h wind gust occurred in Steinbach (not associated directly with a thunderstorm). Wind damage, including downed power lines and downed trees, was reported in the area.
Thanks to a wet second half of September, September was the first wetter than normal month since April in Winnipeg. Only about 305 mm of precipitation has fallen so far this year, making this January to September period the 9th driest since 1873.