Don’t call it a ‘cool down!’

The Weather Authority

…but temperatures do drop a little later this week

Wednesday brings one more day of low-to-middle 90s before a gentle tropical breeze from the southeast drops the temperature a few notches and raises the daily chance of spotty downpours over the next few days.

The day starts warm and muggy: early morning lows around 70ºF with some patchy fog. It gets hot again: back in the 91ºF to 95ºF range with a heat index near 100ºF between noon and 4 PM. A few brief, isolated showers develop between noon and 6 pm, but most of North Alabama and Tennessee stay dry for a fourth-straight day.

The rest of the week: not as hot, more spotty storms

Thursday and Friday won’t be quite as hot as the week started, but we do not see a major ‘cool down’ coming. Temperatures drop with the influence of two tropical waves passing; these are weak ‘disturbances’ that tend to enhance daily thunderstorms, and they bring even more humid air since they’re riding what looks like a conveyor belt of tropical moisture from the Atlantic and Gulf.

Some scattered, hit-or-miss, unevenly-spread, locally-heavy thunderstorms develop here and there on Thursday and Friday. A few high school football games could get rained on (or even have a lightning delay) both nights, but neither Thursday nor Friday appear to be total wash-out kind of nights.

  • Thursday evening games: 30% chance of a storm, temperatures in the upper 70s/lower 80s
  • Friday evening games: 20% chance of a storm, temperatures around 80ºF.

In spite of the daily chance of thunderstorms, average rainfall around here through the next seven days looks about ‘average’ for the final week of August: around or less than one inch with some isolated pockets getting 2-3 inches (added together from multiple downpours).

When do the 90s end?

Climatology tells us a lot: learning the future from the past.

Huntsville’s average final 90-degree day of the season is around September 9th (using data from Huntsville International Airport from 1991-2020).

The latest 90ºF on record came October 23, 1947.

Through Wednesday, we’ve only had 29 days of 90s this calendar year so far. We will probably add a few more before we reach mid-September.

European guidance – the long-range ensemble – gives us a limited chance of 90s as late as October First. This chart shows projected maximum temperatures at 12-hour intervals 45 days into the future (all of the little boxes are the individual temperatures).

There are many more potential outcomes with cooler air than hotter air beyond September 15th, so that gives us a decent amount of confidence in the ‘usual’ Fall temperature trend.

The average high drops from 90ºF to 82ºF, and most importantly, we usually get drier – meaning it’s able to get cooler at night! Lows fall from the upper 60s on September 1st to an average of 58ºF by the end of the month. We usually only get those 50s, though, when it’s less humid and less rainy! This wet summer pattern has to break before any of that fun Fall air can set in for the long haul.

Looking for the rest of the forecast? It’s always online at WHNT.com/Weather and in the “Daily Forecast” section on Live Alert 19!

-Jason
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