The Alabama Climate Report

Brought to you by the Office of the Alabama
Climatologist

Volume 7, Number 10 - July 2017

July wasn't especially remarkable. No station in Alabama reported a daily high temperature record, and only two — Greensboro and Lawson Field — set daily record lows.

In our statewide sample, July was a bit cooler than normal and somewhat drier than normal, although that is an average and we know those can be misleading. Scottsboro got 7.88" of rain, which sets that station's record for July, while three of the 27 stations in our sample got less than 3" for the month. Valley Head — which isn't all that far from Scottsboro — reported only 2.22" of rain in July.

This month, however, is the tenth anniversary of the hottest month in the Alabama climate record. The average temperature for August 2007 was an uncomfortable 84.4° F. That's a full degree warmer than the two months tied for second: August 1954 and September 1930.

But the average temperature doesn't tell the full story of how uncomfortable and hot August 2007 really was. You get that only by looking at the daily high temperatures. And it was baking.

At least 18 stations statewide hit 100° or hotter for a minimum of 13 days that August. The average high for the Montgomery area and Wetumpka was 99.2° and 99.0°, respectively. That included 15 days with high temps of 100° or more.

That wasn't the worst of it. High temps in Hamilton averaged 100.0° that month, including a high of 109°. Pinson, in Jefferson County, and Belle Mina, in southern Limestone County, each averaged a high of 100.1° for the month, and each recorded a monthly high of 107°. Twice.

Belle Mina might have gotten the worst of it, with daily highs hitting at least 100° on 20 days in August, including a stretch of 16 days in a row.

The heat took a toll, with at least 13 deaths in the state blamed on the heat.

When you look at those highs, however, you wouldn't expect to see such a low statewide average, only 84.4°. That was because low temperatures that month weren't that much warmer than seasonal norms.

With daytime highs averaging 100.1°, Pinson's days were 11.4° hotter than normal that August. But the average low for the month was 71.4°, which was only 4.3° warmer than normal.

Poor Belle Mina, which averaged highs 9.3° warmer than its August norms, was only 0.9° warmer than normal at night, with an average low that was a pleasant 64.4°!

Nights in Wetumpka were actually cooler than normal for the month, with an average low of 68.7° compared to the normal low of 70.4°.

That kind of a temperature swing is most often seen in deserts, where 30° and 40° daily temperature swings aren't uncommon. No one is going to mistake Alabama for a desert, but the air that month was dry enough to let the nights cool.

Water vapor is the 800-pound gorilla of greenhouse gases, and water vapor is something Alabama usually has in abundance. That normally keeps our nighttime temperatures from dropping as much as they do in the desert.

But August 2007 was the 15th driest August in the state's climate record. It was part of a severe drought that started earlier in the year and continued into 2008. The dry air allowed a somewhat larger than normal swing in temps, and kept temperatures from being more miserable than they already were.

There's nothing to indicate we're going to see anything like that this August, but it's still a good idea to be prepared.

- John Christy