Wednesday 1 July saw the hottest July day in the UK on record, and of course the population and the media responded with the typical calm and level-headedness you’d expect.

I myself missed most of it as, by astonishing coincidence and following a celebratory pub visit with some friends, I was enduring the worst hangover on record. The sort of hangover where every internal organ is competing for the title of “biggest source of wretchedness”. The sort of hangover where your own skull seems to be angry at you. The sort of hangover where even attempting a sip of water feels like trying to down a cocktail of rancid milk and toilet cleaner.

This isn’t exactly the sort of thing you want to be going through when it’s so hot outside that your car tyres are melting. But I did. Because I’m awesome like that.

For many this would seem like a wasted day, lying on the bed hoping to die for nine hours, rather than going out and enjoying the weather, but according to scientific evidence it may have been the wisest course of action overall. Despite the fact that people (in the UK at least) regularly long for hot weather and will travel great distances to find it, the notion that hot weather makes people more aggressive and violent is a well-known one in the psychology field. You may have experienced it yourself; online discussions taking a more hostile turn faster than normal, people being more short-tempered than usual, even things like the 2011 London riots often take place in high summer.

We have a decent idea of how anger works, and how it spreads far and wide. We also know quite a lot about how humans respond to excess heat. So what’s the link between all these things? Why would hot temperatures make us so hot tempered?

This is a tricky question. The original data, which first provided evidence for this relationship between heat and hostility, came from crime statistics. Many reports and analyses noticed that crimes, particularly violent crimes, increase in occurrence during the summer, especially if it’s hotter than average.

However, there are many things that could explain this; people are outside a lot more during the hot weather, so there is a drastically increased chance of people meeting each other in circumstances that would result in a violent altercation (i.e. if you’re the sort of person who’d pick a fight with someone who spilled your beer, the more people there are the more likely your beer is to be spilled). Also, criminals are often opportunists; thieves will rob homes and steal wallets when the opportunity arises, and it arises more often as people are out and about, enjoying the warmth.

Added to this, schools are closed for summer, meaning hordes of adolescents are left to roam the streets with their rebellious, aggressive tendencies. With all this to consider, no wonder there’s a spike in the stats! Especially in cities, which are usually much warmer than elsewhere.

But according to many, this isn’t enough to explain the actual data. Ergo, it’s widely believed that heat makes people angrier by more “direct” methods. There are numerous theories for why this might happen.

Some argue that the physiological reactions to heat are responsible. Raised temperatures cause an increase in heart rate, testosterone, and other metabolic reactions that trigger the sympathetic nervous system, which is responsible for the fight-or-flight response, so people are more inclined to fight.

There are also numerous psychological theories. One is based on discomfort; unless you have access to climate control technology like air conditioning, it’s very hard to escape the heat. If it’s cold you can wear more layers, but high temperatures follow you everywhere, especially if it’s humid. When people are experiencing discomfort and the resultant stress due to something they have no control over, it makes them angry, and the anger is often displaced onto something else, like someone being irritating in the street.

This has also lead into other applications and theories, like the cognitive neoassociation theory, which argues that people exposed to unpleasant “negative” stimuli will be predisposed to anyone they associate with the unpleasant thing, which in the heat is potentially everything.

A number of experiments have looked into this, with varying degrees of success. This is understandable, it’s very hard to recreate the experience of oppressive, inescapable heat in a lab, which are invariably climate controlled and forbidden from preventing people from leaving. However, some original and inspired approaches have been used, like measuring the tendency of people to honk at traffic lights in certain weather conditions.

Much of the field of psychology is taken up with debating whether the heat equals aggression link declines again above a certain point or not (ie it eventually gets so hot it suppresses people’s actions), but there’s not much to dispute that it’s a real thing, it’s more a matter of how it occurs and what it actually does to us. There are many other possibilities than those mentioned, like how regulating your body temperature requires energy, energy which is no longer available for suppressing aggressive impulses, and thus they occur a lot more in people. Or maybe people are just more angry as they’re not beach body ready and are thus infuriated.

This isn’t to say that anyone who lives in a hot country is automatically more aggressive than those who live at higher latitudes, it’s more to do with relatively high temperatures. In any case, if you’re feeling overheated in the weather, you might want to try keeping a tighter hold on your temper. There’s barely enough cool to go around as it is, you don’t want to go losing yours.

Dean Burnett tends to get sunburn from an overly bright light bulb, so isn’t the biggest fan of heatwaves as it is. He’s on Twitter, @garwboy