Fire Weather/Fire Prevention Awareness Week
concludes Today with a look at the Spring and Fall
Fire Weather Seasons.
As mentioned earlier in the week, low relative humidities and high wind speeds are
two key ingredients which act to increase the degree of
fire danger. These two ingredients, combined with drier vegetation, are
most prevalent during the spring and fall fire weather seasons.
The spring fire weather season occurs in the late winter and early
spring. It begins on February 15th and lasts until April 30th. In
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 on leaf litter and understory
and the high moisture content of growing vegetation brings an end to
the spring fire season. Spring is when the majority of wildfires
The fall fire weather season runs from October 1st through December
15th. Normally for Kentucky, the months of September and October, are
on average the two driest months of the year. This makes September and
October combined the driest two month period during the year on
average. During this time of year, temperatures are also cooler on
average. These cooler temperatures help reduce the threat of stronger
afternoon and evening 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 typically located well north of Kentucky during September
Typically, in the month of September the vegetation becomes drier. By
October, the combination of drier vegetation, falling leaves that dry
out and the end of the growing season sometimes leads to an extended
period of higher fire danger.
Climatological records for Jackson and London indicate that the
driest months on record generally occur in September and October.
The normal rainfall at Jackson for September is 3.46 inches, while
the normal rainfall for October is 3.19 inches. At London, the
normal rainfall for September is 3.37 inches and 3.02 inches for
October. Since 1981 at Jackson, eight Septembers and nine Octobers
have had rainfall of less than two inches. Since 1955 at London,
fifteen Septembers and seventeen Octobers have had rainfall of less
than two inches. In fact, at Jackson, the driest two month
September and October period on record occurred in 2005, when only
2.08 inches fell. The driest two month September and October period
at London occurred in 2008, when only 1.30 inches of rain fell. At
Jackson, the second driest September and October period was in 2008
when only 2.14 inches fell, while the third driest September and
October period occurred in 2001, when only 2.50 inches of rain
fell. Meanwhile, London was wetter during September and October
of 2001, receiving 3.72 inches. Fall 2001 was one of the most
active fall fire weather seasons on record in eastern Kentucky.
Although we have discussed the seasonal impacts of weather on wildfires,
keep in mind that wildfires can occur at any time of the year in Kentucky.
Always strive to stay educated about wildfire prevention. But
most importantly, be careful and act responsibly!
For additional fire weather information, please
visit the following website: www.crh.noaa.gov/jkl/fire.php