Over the past couple of decades, statistics have shown that the number of violent crimes increases in hot months of the year, even in hot hours of the day.

Even though many researchers acknowledge that there are other factors involved, some experts believe that being uncomfortably hot has something to do with aggression.

Richard Larrick with Duke University has completed a study that shows an increase in a specific form of aggression when the mercury rises - retaliation.

His team went through five decades of data from baseball and found that the hotter the temperature, the more likely a pitcher has been to intentionally hit a batter when one of his own teammates was hit earlier in the game.

"As it gets hotter, we become... more negatively aroused," Larrick says research shows. "We essentially just feel irritated."

Other researchers in the U.K. say that they believe violent crime is linked to an increase in stress hormones, which are produced when the body is reacting to heat.