To sense the extent of the change in the weather, one only had to look down – squishy lawns, rain-soaked sidewalks and on this casual Friday, the reappearance of cowboy boots.

RON BASELICE/DMN

A couple walked in the rain through Katherine Rose Memorial Park in Mansfield on Friday.

Like the good, drenching rainfall that added almost an inch of rain to the year's total at Dallas/Fort Worth International Airport, the first such deluge in almost four months, the boots, too, signaled a meteorological shift.

For a day, at least, sandals, slip-ons and other casual footwear gave way to something a little more Texan.

Of course, some Texans, like Mark Fletcher of Plano, swear by their boots 365 days a year.

"I'm in the office a lot of the time," Mr. Fletcher said, "but even when I'm outside, it isn't a problem. I think the scalloped tops keep boots pretty well ventilated."

Still, the sudden shift in the weather had an effect.

True, motorists accustomed to highways baked dry by summer heat found themselves skittering over rain-slick roads. And early risers found a hint of a chill in the air, if 70 can be chilly.

Even the National Weather Service Web site exulted in the change: "Any time early afternoon temperatures are in the upper 70s to mid-80s in August is certainly a rare treat."

But is this the sort of treat that lingers for a while, or disappears as quickly as it arrived?

That depends on which computer model is correct.

"There are some indications that the upper-level low might stick around for most of next week," said meteorologist Nick Hampshire, "which means more cooler, wetter weather. But there are other indications that it will be gone by Tuesday night, and we'd warm up again."

To many, though, there's been warmth enough this summer, with average high temperatures in July falling just shy of 100, and the first 14 days of August even warmer, with an average high of 100.9.

But then came the 15th, with showers across much of the Dallas area and clouds lingering into the morning, capping temperatures in the 80s, even mid-80s in some spots, about 10 degrees below normal for the date.

High temperatures could remain in that range through Tuesday before nudging into the 90s by next weekend.

"We could get rain each day," Mr. Hampshire said, "but the best chance is Monday, when the low is closest to us."

That means the weekend could be a great chance to get outdoors, particularly good news for those who suffer from "the summertime blues."

Seasonal affective disorder, well known to psychologists and psychiatrists, usually refers to people who suffer in winter, and mostly in the higher latitudes. There is a reverse of that, though, which affects some in the heat of summer.

But the causes of summertime depression are less clear. Dr. Madhukar Trivedi, professor of psychiatry at UT Southwestern Medical Center, suggested one possibility.

"Some people who have depression seem to be able to self-manage that through physical activity," he said. "But in the summer months, when it's very hot, they might not be able to engage in that activity. They can't do what they normally do to stave off depression, and their symptoms reappear."

But when the weather cools, people get more active again.

And physical activity, Dr. Trivedi said, is good for everybody.