Fire danger increases along with temperatures
July is one of the driest months of the year in the Inland Northwest.
Spokane averages about .76 inches of rain in July, with Coeur d’Alene averaging .96 inches. So far , only a trace (less than .01 inches) of rain has fallen at the Spokane airport, though a few thunderstorms have brought nearly half an inch to Coeur d’Alene this month.
Fire season is a bit late getting into full swing around here due to the unusually cool and wet spring, but the current string of hot and dry days will definitely increase the fire danger as area vegetation begins to dry out.
One of the things that used to puzzle me when I read about lightning-induced wildfires was the fact that many times the radar would be lit up not only with the indication of lightning strikes, but of rainfall as well. You wouldn’t think that a raging wildfire could be born under a torrential rainstorm.
Though the term “dry lightning” is often used to describe these wildfire-sparking storms, the words are misleading. A dry lightning storm is not necessarily rain-free, but can drop up to 1/10 of an inch of rain. Rainfall of less than .1 inches doesn’t do a whole lot to hinder a growing fire. The term “wetting rain” is used to describe rainfall amounts of more than .l inches.
Red flag warnings are often issued this time of the year by the National Weather Service to indicate the potential for dangerous fire weather. This would include conditions such as dry lightning, but also conditions such as strong winds or perpetually low relative humidities that could make existing fires more dangerous and difficult to control.
The triple whammy usually occurs ahead of a cold front. The hottest temperatures occur just ahead of the front, with maximum heating and drying effects. As the front moves through, storms can develop – many of which are the “dry lighting” type bringing little to no rain. The final blow comes behind the front, where temperatures might be cooler but winds may be howling. Fire weather forecasting in the region is difficult due to significant variations in wind speed and direction as a result of the terrain.
Once large fires get going, the heat from the fire begins to exert a strong influence on the atmosphere around it – to the point of being able to instigate new thunderstorms. Meteorologists from area Weather Service offices can be deployed directly to the location of large wildfires to provide on-site weather support to firefighters.
The upcoming week continues to look dry, with the potential for several scorching 90-plus degree days. Triple digit heat does not look likely. Last year in Spokane, high temperatures hit 101 degrees on both July 5, and 13. The year before that saw three consecutive days of 100-plus degree temps (the highest was 102) from July 22 to 24.