Wednesday, June 21, 2006 | 7:17 a.m.
When temperatures rise in Las Vegas - remember last July's record-breaking 117? - so do tempers.
Researchers point to a summer swell in reported assaults as evidence that heat and hostility are joined at the hip.
"People probably behave in ways they otherwise wouldn't," says Sgt. Matt McCarthy of Metro's Violent Crimes section. "As the summer months encroach upon us, our crime rate does seem to go up, and it's usually just in cases where folks just don't get along."
Metro doesn't crunch numbers on warm-weather crime. The FBI's compilation of 2004 crime statistics, however, shows that reported assaults in Las Vegas rose with the thermometer, picking up in May and tapering off by October. Assaults were highest in June and July, when the average high readings regularly top 100 degrees.
Incidences of misdemeanor battery and assault increase with warm weather, though the trend may have much to do with secondary effects: more people outside more often, and more people drinking alcohol, McCarthy says.
"You could draw the conclusion that people are more aggressive," he says.
Just being uncomfortably hot is enough to make a person mad, according to Iowa State University psychology professor Craig Anderson, who has studied the connection between heat and violence.
Research shows that heat can make people hostile and, with provocation, more willing to hurt someone, he says. In a 2001 article on the subject, Anderson wrote: "Aggression - as measured by assault rates, spontaneous riots, spouse batterings, and batters being hit by pitched baseballs - is higher during hotter days, months, seasons and years."
Metro traffic officers are accustomed to encountering particularly agitated drivers at summer auto accident scenes, Sgt. Tracy McDonald says. The problem starts when collisions leave Las Vegas drivers stranded on the side of the road without water or shade.
"It's every year - they're waiting in the intersection, they're not prepared, they don't have any water," he says. "Sometimes you get to scenes and they're actually suffering through dehydration and heat stroke."
The hot weather is also connected to a seasonal rise in home invasions, robberies and burglaries, according to Lt. Mitch Bradshaw.
"The hotter someone is, any time it's more uncomfortable, it's just a human factor - people tend to have shorter tempers," he says.
And people tend to leave their windows open.
"During the summer, people want to save on their power bill, let the wind blow through the house for fresh air, and with this always comes the opportunity," Bradshaw says.
"If I'm a crook, I'm going to go where the fishing is good."
Bradshaw estimates the number of sexual assaults on strangers grows by 10-15 percent during the summer months. The victims are most often single women or senior citizens who have left their balcony doors and windows ajar for whatever breeze the valley brings.
Without air conditioning, Las Vegas apartments can quickly approach unbearable - a lesson that's not lost on criminals, or the SWAT team, who also use the rising thermometer as a means to their own ends.
In dark jumpsuits and up to 70 pounds of gear, SWAT officers try to sweat criminals out of hiding without overheating themselves.
"It's not just the bad guys' comfort level. We're all human - the weather impacts our fatigue, our emotions," Metro SWAT Sgt. Bret Empey says. "People become agitated. In the summer, it just happens a little quicker."
So the team uses a simple, but effective, technique to coax suspects out of hiding in buildings when the mercury mounts.
They cut off the air conditioning.
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