City of Chilliwack August 2020 Weather Review – Below Average Rainfall, Warm (Remember That Chilly Start to July?)

Chilliwack – (Roger Pannett – Environment Canada) – August 2020 was below average in rainfall according to the Data recorded by Roger Pannett, Volunteer Weather Observer for Environment Canada at the City of Chilliwack.

Chilliwack was a little warmer than usual although it could have been worse. Remember the start to July!?!?

VariableAugust 202030 Year Average
Mean Maximum25.69 C23.9 C
Mean Minimum13.87 C11.9 C
Mean Temperature19.78 C17.9 C
Rainfall42.0 mm64.8 mm
Total Precipitation42.0 mm64.8 mm
Days of Rain8 days9 days
Days of Snow
Total Days of Precipitation8 days9 days
Relative humidity average64.72 %

As a ridge of high pressure remained in place off the Washington state coast, the hot & dry conditions of late July continued into early August. During the passage of three cold fronts, (two of them active with an associated unstable air mass), welcome rainfall occurred at the end of the first week, soon after mid- month and at months end.

On August 16th, a strong ridge of high pressure with clear sunny skies produced record heat at 35.8⁰C (24% relative humidity) and the hottest temperature of the summer. Four high temperature records occurred:

Date New Record Previous Record

August 16th High Max 35.8⁰C (+12.1⁰C). 35.6⁰C in 1977.

August 16th High Mean 25.9⁰C (+8.4 ⁰C) 24.8⁰C in 1977.

August 17th High Min 20.4⁰C (+9.1 ⁰C) 17.6⁰C in 2013.

August 17th High Mean 26.25⁰C (+8.85⁰C) 25.6⁰C in 1977.

There were 3 hot days with temperatures exceeding 30.0⁰C, (the lowest number of August hot days in 7 years), compared to the average 2 hot days with a + or – 2.7day standard deviation.

On August 30th, beneath clear skies, the minimum temperature for the month was 9.5⁰C the coolest August night in 8 years.

Unlike Vancouver Island, which experienced severe thunderstorms during the evening of August 16th, the hot unstable air mass did not trigger any eastern Fraser Valley thunderstorms.

On the evening of August 21st, the passage of an active cold front produced a heavy rainfall of 19.3 mm with gusty west winds. However, rainfall totals for the month remained at 35.2 % below normal, the 5th consecutive August with below normal rainfall.

The City of Chilliwack 2020 precipitation total to date is 926.7mm on 126 days compared to the average of 1,047.8 mm on 106 days.

With mean temperatures 1.88°C above normal, it was the 20th consecutive August with above average mean temperatures, including the 9th consecutive year with temperatures in excess of the + or – 1.2°C standard deviation.

Since 2012, August mean temperatures have been 1.88°C to 3.87°C above normal, a warming trend never previously observed in the past 125 years.

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