It's often suggested that increased ambient temperatures tend to increase aggressive behavior in humans. There is, however, no generally agreed explanation for the phenomenon.

See: ‘Ambient Temperature and Horn Honking : A Field Study of the Heat/Aggression Relationship’ ^{[ paywalled ]} in: Environment and Behavior, March 1986 vol. 18 no. 2 179-191.

A BBC 'Fact Check' feature (July 2018) lists various studies that confirm that there tend to be more reports of violent crime as the temperature rises.

Experts divide the reasons into two main categories:
• The physical effects of heat on people's responses
• A change in the opportunities available to commit crime
Heat is an irritant and the discomfort it causes might make people shorter tempered. "

See: Heatwave: Is there more crime in hot weather?

Also see: Testosterone and aggressionplugin-autotooltip__plain plugin-autotooltip_bigTestosterone and aggression

""Little is known about the neurobiological pathways through which testosterone promotes aggression or about the people in whom this effect is observed."

Source : Using a Psychopharmacogenetic Approach To Identify the Pathways Through Which-and the People for Whom-Testosterone Promotes Aggression"

This 2019 study published in the journal Psychological Science