It’s no surprise to learn that Chilliwack has just gone through the driest summer on record.
How dry?
Rainfall was 94.6 per cent below normal, according to Roger Pannett, volunteer weather observer for Environment Canada.
“It was the driest August since 2012,” he noted in his August weather report. “With a July and August combined total of 12.5 mm, it was the driest since the meagre 2.6 mm in 1930.”
But it was the lack of rain from June to August, totalling only 48.5 mm that is notable.
“It was 75 per cent below normal,” said Pannett, making it the driest since Chilliwack precipitation records began in 1879.
The previous driest was in 1919 at 54.4 mm.
The unrelenting drought and heat has resulted in many Chilliwack trees suffering premature leaf shedding and branch splitting.
To date Chilliwack precipitation total is 829.3 mm on 109 days compared to the average 1,047.8 mm on 106 days.
So how hot was it?
During the three separate heat waves there were 12 days with temperatures of more than 30 C – the most ever recorded. The air quality health index was at 7, meaning poor air quality, for several days in a row.
The 30-year average is two days of more than 30 C with a 2.7 day deviation.
Pannett said with re-occurring upper-level high pressure ridges throughout August deflecting Pacific frontal systems and associated moisture to northern B.C., the unusually dry and hot summer conditions persisted.
“Thermal outflow conditions, coupled with the worst forest fire situation ever experienced in the province, produced a record breaking 11 consecutive days of poor air quality advisories,” said Pannett.
There were only a couple of days of light showers to help clear the air.
With a mean temperature 3.88° C above normal, with a + or – 1.2° C standard deviation, it was the hottest August since Chilliwack temperature records commenced in 1895.
Also it was the 17th consecutive August with above average mean temperatures, including the 6th consecutive year with temperatures in excess of the 1.2°C standard deviation ( 2.06°C to 3.88°C above normal).
Temperature extremes for August and the summer of 2017 were the record breaking max of 35.6° C (19 per cent relative humidity) with smoky conditions on August 2 and a mild low of 11.6° C on August 15.
Mid-morning, on August 21, with clear sunny skies temperatures temporarily dipped 1.1°C 20 minutes after the peak of the 0.89 magnitude eclipse.
@chwkjourno
jfeinberg@theprogress.com
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