I’m in British Columbia and for months the experts have been saying how bad the drought is here, it’s going to be a rough summer, bad crops, etc. We have had a fair amount of rain the last couple of weeks but I’ve still had to water on the few sunny days. Now tonight they show the wild fire risk is low in most areas or moderate. Precious years it has taken a lot more rainy days to see the risk drop. What am I missing?
In: Planetary Science
From what I understand, rainfall is only one factor in determining fire risk. I believe low humidity, high temperatures, and high wind speeds are also factors that go into assigning risk.
Drought risk in BC is a combination of snow pack and rain fall.
Outside of the coastal areas, many interior forests rely on snow pack to keep the soil moist until June or July and to fill reservoirs, rivers etc. There has not been that much snow this past year. Disturbingly little. So the ground will dry out quickly once it stops raining.
In spring, everything is growing, sucking water out of the ground and into trunks and leaves. It’s hard to burn because the vegetation has so much water.
But between less snow and far less rain in the spring, and much warmer temperatures than usual, it’s easy to see how the ground and vegetation is going to dry out much faster than usual.
In the lower mainland, we are about three weeks early for spring. We are experiencing weather and plant growth we would normally see in June. There hasn’t been as much snow and our rivers are much lower than normal. It is freakishly dry – I know it rained recently but since February 2023, it has been consistently drier than I ever remember. I’ve lived in this area for about 40 years.
Fire risk takes many components into account. Wind, more wind higher risk because it provides more air to fires and spreads embers farther. More humidity makes it harder to ignite material. Rainfall. I worked at a boy scout camp in the Sierra Nevada mountains and we had a fire ranger giving a lecture at the beginning of camp. He talked about day, week, month and year times for vegetation. Small stuff like leaves or pine needles dry out quickly so they might take one day to dry out. Bigger branches perhaps a week. The bigger they are the longer they take to dry out. The big stuff isn’t going to dry out for awhile. Also the growth the season before matters. Wet years build up more vegetation so a drought following a wet year is riskier than a moderate year followed by a drought because there is more fuel laying around.
My wife works in wildfire meteorology.
Moisture is only one component that determines how likely a wildfire is to (a) start and (b) spread. Note that (b) is far more concerning. A fire that doesn’t go anywhere is easy to control.
Other components include:
* wind
* temperature
* terrain
* dry fuel abundance (e.g. how much dry dead growth is around to burn, which can be very much independent from whether or not we are in a drought)
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