Heat Warning Thresholds are Garbage

[Glacier]

This week the only place in BC under a heat warning is Clearwater, not because it's hotter than everyone else (it's not), but because the threshold to trigger a warning there is so low. Even though it's 2000 ft lower than 100 Mile and Clinton, it only needs to have a forecast of 29C in the day and 14C at night, just like Clinton and 100 Mile. The summer climate is like Salmon Arm, but in Salmon Arm the temperature needs to be 35C in the day and 18C at night.

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Also, Sparwood and Yoho National Park also need to be 35C/18C to trigger a warning, which has never happened in those high elevation places, so they cannot get heat warnings.

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BTW, I just did a quick search for various places in BC. I set the search function at 0.5C below the thresholds so temperatures are rounded to the nearest degree C.

Clearwater (with data only going back 6 years) averages 1.2 heat warning days per year (I only start counting after 2 days in a row meet the threshold).

Abbotsford averages 0.11 days per year (with data going back to 1942). The threshold in Abbotsford is 33C and 17C.
YVR averages 0.15 days per year (data started in 1937. The threshold for Vancouver is 29 and 16)
YYJ averages 0.22 days per year (data started in 1915)

Other places:
Cranbrook = 0.02 days per year (only one occurrence since 1969, and that was in 2006)
Williams Lake = 0.34 days per year (1/3 of those days occurred in 2009)
Lytton = 1.7 days per year (looked back to 1994)

Terrace = 4.3 days per year!!!!(data back to 1953)

In the case of Terrace there's a heat warning triggered almost every year, but for all the others you get a few heat warning days one year and then nothing for years and sometimes even decades.

[Abby_wx]

Yeah, total nonsense. We had a thread about this a while back... I'm not sure what happened to it.

YVR's overnight threshold is a degree cooler than YXX's, yet YVR is normally slightly warmer than YXX at night. You can see this by comparing the average minimums for the summer months, and also during heat waves. In July 2009, for example, YVR was either the same or slightly warmer at night compared to YXX. In fact, YVR averages 1.5C - 1.8C warmer at night than YXX in July and August.