Chilliwack ( Roger Pannett, Volunteer Weather Observer for Environment Canada at the City of Chilliwack) – The dry, warm and sunny conditions of late September continued into the first week of October, as a strong upper level ridge of high pressure deflected the jet stream to northern British Columbia. Temperatures for the month peaked at 24.5⁰C (6.8⁰C above normal) on October 2nd, the warmest October day since the 26.0⁰C on October 6th, 2012. Freezing levels rose to 14,500 feet, but skies were also hazy because of high level smoke coming from Californian wildfires.
On October 8th, typical fall weather conditions returned with a heavy rainfall of 56.9 mm on October 9th. With a mild, moist south westerly air flow there were two overnight high temperature records observed: –
Date. New Record. Previous Record.
October 8th High Min 13.7⁰C (6.7 °C above normal) 13.0⁰C in 2015.
October 9th High Min 13.5⁰C (6.8°C above normal) 13.0⁰C in 1979.
For the next two weeks a series of fast-moving Pacific frontal systems produced periods of rain and with falling freezing levels, high elevation mountain snowfalls. On October 13th, high winds gusting up to 74 km/hour produced widespread power outages.
With the passage of a low-pressure system, passing just off Vancouver Island and moving onto the Washington coast, modified arctic air advanced south wards through the B.C. Interior. On October 23rd a heavy snowfall closed the Coaq for several hours. In the wake of the low-pressure system a drying trend developed, for a few days, as modified arctic air with cold outflow winds occurred.
Three low temperature records were observed: –
Date New Record Previous Record.
October 24th Low max 6.5⁰C (6.3⁰C below normal) 6.7⁰C in 1934.
October 25th Low max 5.5⁰C (7.4⁰C below normal) 6.1⁰C in 1975.
October 25th Low mean 2.55⁰C (6.75⁰c below normal) 2.8⁰C in 1919.
There were two frosts with temperatures dipping to -0.4⁰C, plus wind chill, on October 25th. On average the first frost of the season occurs, in Chilliwack, on November 9th. In 2020 there were 203 frost free days compared to the average 216 frost free days.
After some wet snow, during the early hours of October 26th, weather conditions returned to normal with the month concluding with clear, sunny skies and mild temperatures.
With mean temperatures 0.67⁰C above normal it was the warmest October since 2015.
The City of Chilliwack year to date precipitation totals are 1,155.1mm on 154 days compared to the 30-year average of 1,346.7 mm on 133 days.
| Variable | October 2020 | 30 Year Average |
| Mean Maximum | 14.89 C | 15.3 C |
| Mean Minimum | 8.45 C | 6.7 C |
| Mean Temperature | 11.67 C | 11.0 C |
| Rainfall | 149.1mm | 186.1 mm |
| Snowfall | 0.8 cm | 0.1 cm |
| Total Precipitation | 149.9 mm | 186.2 mm |
| Days of Rain | 18 days | 16 days |
| Days of Snow | 1 day | – |
| Total Days of Precipitation | 19 days | 16 days |
| Frosts | 2 | 0.9 dev’ |
| Relative humidity average | 74.19 % | . |
