Extreme Heat and Humidity Persist Across the Southern U.S.

Quincy Vagell
Published: August 9,2015


 

On the heels of a hot finish to July across much of the southern U.S., another string of hot days is underway. Through early this week, triple digit heat will continue to bake much of the Southern Plains and Lower Mississippi River Valley. As of Sunday evening, more than 30 million people were under heat advisories or excessive heat warnings across those regions.

Current Temperatures/Feels Like Temperature

Three-Day Forecast Highs

If 100-degree heat was not bad enough, high levels of humidity will make it feel even more uncomfortable.

Forecast Feels Like Temperatures

With dewpoints forecast to remain in the 70s for several days, the heat index – or the temperature it feels like when you factor in the humidity – is forecast to rise to near or even above 110 degrees in many locations into Monday. The hardest hit areas will be across Oklahoma, Texas, Arkansas, Louisiana, Mississippi, Alabama and western Tennessee.

On Sunday, the heat index peaked at 114 degrees in Little Rock, Arkansas. Equally as miserable was Tulsa, Oklahoma, where the heat index was 112 degrees in the late afternoon. Tulsa recorded its first 100-degree day of the year on Friday and was in the low 100s both Saturday and Sunday.

Little relief is expected at night as cities like Memphis, Tennessee, and Jackson, Mississippi, may struggle to fall below 80 degrees for low temperatures through Tuesday morning.

(MAPS: 10-day Forecast)

While some daily record highs may be broken, the bigger story may be the longevity of such hot conditions. Shreveport, Louisiana, did not hit 100 degrees even once in 2014, but they have already reached 100 degrees 14 times this summer. This includes a stretch of 14 out of 17 days from July 24 to Aug. 9. 

Daily record highs may be challenged in the following cities the next couple of days (current record is in parentheses):

• Monday: Jackson, Mississippi (103 degrees); Houston (104 degrees); New Orleans (97 degrees)
• Tuesday: Shreveport, Louisiana (103 degrees); Jackson, Mississippi (103 degrees); Houston, (102 degrees)

The hot weather is associated with a ridge of high pressure in the upper levels of the atmosphere. This ridge is centered right over the southern Plains right now. However, it is influencing a broad area of the South with sinking air motions that suppress thunderstorm development. This will deflect most rain and thunderstorm activity to the north, meaning much of the period will not only be hot, but short on rainfall as well.

Rainfall is one thing several Texas cities saw none of in July. The city of Tyler, Texas, marked its first rainless July since continuous recordkeeping began at the airport in 1984. Longview and Waco each had their first rain-free July since 1993. Waco has had 39 straight days with no rain through Saturday, which is the longest dry streak there since 1952, according to the National Weather Service. In Louisiana, Monroe just experienced one of its top 10 driest months of July on record.

(FORECASTS: Dallas, Texas | Baton Rouge, Louisiana)

Even locations very close to the Gulf Coast, including southern Louisiana, are feeling the effects of the oppressive heat and humidity. Being east of the high-pressure center means winds will tend to blow from the north. While that's a cold wind in winter, it's a wind blowing off sun-parched land in summer and preventing the moderating effects of the Gulf of Mexico from having as much of a cooling influence.

Some relief is possible by the second half of this week as some forecast models shift the ridge farther west, taking the hottest of the hot air with it. For example, highs may retreat back into low 90s or upper 80s in parts of Arkansas, Oklahoma and west Tennessee by Tuesday or Wednesday.

(MORE: Severe Heat in Middle East | How Hot is Too Hot?)

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