September 4, 2015, Heavy Thunderstorms and Extreme Humidity
It was a hot and very humid start to September in 2015. The first three days exceeded 30°C and dewpoint temperatures exceeded 20°C from the 2nd to the 4th. In fact, on the 3rd and 4th, dewpoint values reached a record 23°C, the second highest recorded in September since 1953. Humidex reached 42.0 on the 3rd, the second highest on record in September since 1953. All the humidity culminated in an active thunderstorm day on the 4th.
It was a very warm and humid night on the 4th. Temperatures hovered near 25°C most of the night, and did not drop to 23°C until mid morning. Thunderstorms developed across southern Manitoba during the overnight hours and dropped large hail. Hail up to toonie-sized fell from Niverville and Ile-des-Chenes to Cooks Creek just east of Winnipeg. Up to dime sized hail was reported in eastern parts of Winnipeg around 2 am.
It was in the afternoon that the heaviest thunderstorms developed. Locally, over 50 mm fell in the Red River Valley. The Winnipeg area was one of the hardest hit areas with 30 to 50 mm of rain in just under an hour and wind gusts over 80 km/h. The storm struck around 2 pm and it was dark enough for street lights to become illuminated. Significant street flooding occurred, including flooded underpasses. The underpass at Logan and Route 90 was shut down for hours due to flooding. With more rain later in the day, daily totals were between 40 and 60 mm. The airport recorded 41.1 mm for the day, breaking the old daily record of 36.8 mm in 1872. About 31 mm had fallen in an hour, the second highest on record in September. The Forks recorded 38 mm in an hour. The storm resulted in the cancellation of a concert at Assiniboine Park and the baseball game at Shaw Park. Four West Jet flights were diverted to Brandon as a result of the storm, before they could land in Winnipeg.
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| From the Winnipeg Free Press Sep 5, 2015, page 4 |
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| Cocorahs rainfall amounts Sep 4, 2015. Click to zoom in |
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