OUR PRIMARY AND SECONDARY FIRE WEATHER SEASONS


Low relative humidities and high wind speeds are two key ingredients which act to increase the degree of fire danger. These two weather ingredients, combined with drier vegetation, are most prevalent during the primary and secondary fire weather seasons.

The primary fire weather season occurs in the late winter and early spring from February 15th until May 1st. In late February and March, most of the vegetation is still dormant as temperatures begin to warm. Lengthening daylight hours and warmer temperatures increase the surface temperatures, and in combination with higher wind speeds, dry out the vegetation. With these ingredients in place, elevated levels of fire danger typically occur until the forest foliage is at full growth and providing shade. The cooling effect of the shade and the high moisture content of growing vegetation brings an end to spring fire season. Springtime is when most wildfires occur.

The secondary fire weather season occurs typically from October 1st until December 15th. Normally for Tennessee, the months of September and October are the driest months of the year. During this time of year, temperatures are also cooler. These cooler temperatures help reduce the threat of heavier showers and thunderstorms, which are usually triggered by warmer surface temperatures. Also, the jet stream, which brings better-organized weather systems with more widespread rainfall, is located well north of Tennessee. Typically in the month of September, the vegetation becomes drier. By October, a combination of drier vegetation and the end of the growing season sometimes leads to an extended period of higher fire danger. Even though the number of wildfires is usually less than in the spring, the largest fires on record have occurred during the fall, especially after a prolonged drought similar to that of 2007.

Although we have discussed the seasonal impacts of weather on fires, keep in mind that fires can occur at any time of the year. We should always strive to stay educated concerning wildfire prevention. But most importantly, be careful and act responsibly!


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