“Bugs love it here,” says Charlie Wax, state climatologist at Mississippi State University in Starkville, Miss. “We’ve set up the perfect conditions for pests to flourish, and all kinds of pests respond favorably to the weather conditions here. At times it seems that we’ve got bugs and weeds as bug as we are, and they can even move rocks to get to where they want to be. It’s all due to the amount of energy and moisture in our climate.”
In turns out, the same conditions that cause people to wilt after only minutes under the mid-summer Delta sun are also what make the Delta the ideal place for insects to live.
Insects respond to conditions of temperature, humidity, dew, rain, fog, cloudiness, light, wind, frost, and number of hours of saturated moisture with temperatures over 60 degrees, Wax told attendees at the 2003 Joint Pest Management Meeting in Greenville, Miss.
“Their ideal habitat offers warm temperatures and high humidity, with periods of rainfall and dew,” he says. “It’s pretty often that we have 100 percent humidity every night during the growing season, which is very favorable to pests. We also have fog and dew almost every night during the growing season.”
The weather in Mississippi in not moderate. It’s a harsh, feast or famine climate, Wax says, “We’ve got to deal with both mid-latitude factors and tropical factors because of where we are located. It’s a fight every day between the weather to the North and the weather to the South.”
Competing climate factors affecting the Delta’s weather include the Bermuda High, trade winds coming from one side and westerly winds coming from the other, and a continent to the north competing with the Gulf of Mexico to the south. Mix in frontal passages, hurricanes, thunderstorms, and tornadoes, and you’ve got a recipe for considerable climate variability.
“Climate controls including latitude, land-water surfaces, air masses, wind/pressure systems and storms deliver to Mississippi the characteristic weather conditions that we know, and in which we toil,” Wax says. “We get a little bit of everything because of where we are located.”
In addition, larger scale factors such as global and hemispheric climate controls and hundred year trends also play a role in the southern climate. The Mid-South also experiences a type of funnel effect because we are located between large mountain ranges in the eastern United States and the Western United States, allowing cold air to travel straight into the Gulf of Mexico
Temperatures in the central Delta range from minus 2 to 101 degrees F, with an average of 10 days below 20 degrees F in each year. Annual precipitation in the region ranges from 48 inches to 66 inches, with anywhere between 50 and 70 thunderstorms likely each year. Mississippi also experiences about 20 tornadoes per year mostly during the months of February, March and April.
“Tornadoes are mostly a North American phenomenon, and we are right there in the middle of it due to the funnel effect. We’re right under the low, and right under the cold front,” Wax says.
With temperatures and rainfall amounts all over the map, about the only thing “normal” about the Delta’s climate, according to Wax, is its considerable variability. “We have a feast or famine climate, and that’s never good.”
Looking back at historical weather data from 1895 to 2002, temperatures and rainfall departures from normal in the lower Delta (Greenville, Miss.) region are all over the place on the chart. “We can have a very warm year, and then a very cold year the next year. It’s not uncommon for us to see drastic inter-year variability,” he says.
For example, during the 1990 decade, two years were dryer than normal and eight years were wetter than normal. During this same 10-year period, four years were warmer than normal and six years were cooler than normal. That data, Wax says, doesn’t do much to support global warming theories.