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July is usually our wettest month

By Skip Rigney

We are headed into what is usually our wettest month of the year, after a June that was wetter than normal in Pearl River County. That’s according to data from the National Oceanic and Atmospheric Administration, the Southeast Regional Climate Center, and the Community Collaborative Rain, Hail and Snow Network.
The average rainfall for June for the 30-year period between 1981 and 2010 was 5.69 inches in Picayune, 5.57 inches in Slidell, 5.35 inches in Poplarville, and 5.05 inches in Wiggins. In the month of June that ended this past Tuesday, rainfall totals across the county ranged from just under six to nearly ten inches. In the southern part of the county, over half of June’s rain came June 6-10 from Tropical Storm Cristobal, which moved from the Gulf through southeast Louisiana.
June 2020’s temperatures averaged out to near normal across south Mississippi and adjacent portions of Louisiana and Alabama. Our “coolest” afternoons were June 7th and 8th when the clouds and rain from nearby Tropical Storm Cristobal kept us from getting above the lower 80s.
July and January are the two months that our daily temperature averages are virtually the same at the end of the month as at the beginning. In other words, there’s usually no noticeable warming or cooling trend. The month starts hot and ends hot. The historical average low temperature each day in July for both Picayune and Poplarville is 71 degrees and the historical average maximum temperature each day is 91 degrees.
The warmest temperature on record for Pearl River County is 105 degrees, which occurred at the Poplarville Experiment Station on July 16 and 17 in 2000. The weather maps for those dates show a classic July heatwave pattern. A large, strong dome of high pressure in the upper atmosphere over Texas was associated with an area of 100 degree temperatures covering over half a million square miles from New Mexico to Nebraska southeastward to Alabama and Florida. The only other 105 degree observation in Pearl River County was on August 25, 1990, in Poplarville.
The coolest temperature on record for July in our county was 57 degrees in Picayune on July 15, 1968, when an unusual midsummer cold front swept down from Canada all the way into the Gulf of Mexico.
Warm air is able to hold more water vapor than cooler air. In July the atmosphere is loaded with water vapor from the nearby Gulf of Mexico. Add intense daytime heating, and it’s very easy to bubble up afternoon showers and thunderstorms. In fact, they occur an average of 13 days during July. Only August has as many days with rain. Although most of these showers are brief, the efficiency of these rain producers make July’s six and one-half inches the highest monthly average rainfall of any month of the year in Pearl River County.
That’s just the average. July can be even soggier. Thirteen years out of the 92 on record for Poplarville, July rainfall has exceeded ten inches. At the other end of the spectrum, drought can occur in July. In 1924 Poplarville received just under one inch of rain the entire month.
NOAA’s Climate Prediction Center says the odds slightly favor a warmer and wetter than average July 2020 for the southeastern United States.