FORT WORTH -- When the mercury rises, tempers flare.

Drivers honk more. Spouses argue. Strangers can be downright rude.

"There is a connection between heat and violence," said Wade Rowatt, an associate professor of psychology and neuroscience at Baylor University. "When temperatures are hotter, people are more irritated and hostile and likely to be aggressive."

So on Thursday, if North Texans seemed a little nicer, a bit more polite, there was good reason: For the first time in 40 days, temperatures did not reach 100 degrees -- and some areas even saw a little rain.

But, officials say, those sunny dispositions will likely be gone today, with temperatures expected to surge back into the triple digits.

"Stay hydrated, stay inside and take frequent breaks," Rowatt said. "If people feel themselves starting to get angry, take deep breaths."

Maj. Paul Henderson, a spokesman with the Fort Worth Police Department, said assaults and domestic violence spike when it's hot, which is why police try to get in front of the problem by putting more resources in high-crime areas during the summer. And while overall crime is down compared with last summer, Henderson said, aggravated assault and domestic offenses are up, which he attributes, in part, to the excessive heat.

"People tend to be more agitated and irritated with this amount of heat," he said. "We are praying for in a break in the weather pattern."

So is Mary Lee Hafley, CEO of SafeHaven, Tarrant County's largest family violence shelter, which took in 14 families last weekend -- unprecedented for a two-day period. She believes that the scorching summer has something to do with an uptick in domestic violence victims.

"When you get overheated, you get grumpy and your ability to filter your behavior is reduced," Hafley said, "so oftentimes -- while it does not cause domestic violence -- it may lead to more violent episodes or more frequent episodes."

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