Kirsten McDougal, of Round Rock, and Josh Paker, of Austin, show their patriotic colors before last year’s Austin Marathon & Half Marathon. JAY JANNER / AMERICAN-STATESMAN


Consider packing a squeegee if you’re running this weekend’s Austin Marathon and Half Marathon.

Weather forecasters are calling for lows around 60 and highs around 80 on Sunday, with a chance of light showers in the morning and heavy storms in the evening. It’ll be muggy, too, with humidity of 80 to 90 percent as moisture moves in from the Gulf.

That’s not exactly ideal if you plan to run 26.2 miles.

Tyler Olson and Wende Parks finish the Austin Half Marathon together in downtown Austin on February 14, 2016. JAY JANNER / AMERICAN-STATESMAN


Perfect marathon conditions are generally considered colder and crisper, although they vary depending on the runner’s weight and fitness level, course difficulty and other factors.

Most studies indicate that elite runners perform best when temperatures are in the mid 30s. Mere mortals prefer warmer temperatures – somewhere are 47 or 48 degrees – but not as warm as we’ll see Sunday.

Runners World explains the science of it in this article. Shape Magazine chimes in on the issue too, suggesting that ideal conditions for women are 45 degrees and overcast.

Here’s the deal: The faster you run, the more body your heat generates. Cold air helps dissipate heat, but if it’s too cold your muscles will have to work harder to produce energy. Fitter folks can adapt more easily to a wider range of temperatures.

Experts say temperatures that are 9 degrees hotter or colder than ideal slow runners by less than 1 percent; they also say a difference of 18 degrees can slog you down by almost 3 percent. Read more in this article by John Davis at Runners Connect.

Kevin Babb of Austin celebrates as he crosses the finish line at the 2016 Austin Marathon. JAY JANNER / AMERICAN-STATESMAN


Want specifics based on how fast you run? Check this calculator to help determine your ideal running temperature, based on distance and pace. 

In a nutshell, then, most folks run their best when it’s nippy but not bone-chilling cold. And if you’re watching from the sidelines and feel comfortable just standing or walking, the runners are probably suffering.

So, sorry about this weekend, runners. Just hold on to this one bit of good news – no hail or tornados are expected.