Most people would agree that the weather can affect our mood and even our behaviour. After weeks of rain, a sunny day can feel uplifting, while a return of dark clouds can bring on gloom and even depression. Yet while reactions to weather are generic, individual responses can vary greatly; so much so, that it is difficult to draw any firm conclusions about the weather’s influence on human psychology. 


One person who has made a concerted effort to do so is Trevor Harley, Emeritus Professor of Psychology at the University of Dundee in Scotland. Harley has combined his twin passions of psychology and the weather by becoming one of the world’s few psychometeorologists. Harley’s fascination with the weather began in his youth. Among his earliest childhood memories are experiencing a violent thunderstorm, and of feeling awestruck by the transformation a heavy snowfall made to the world. He has been monitoring the weather around his home in Dundee (Scotland) for twenty-seven years. Given, he says, that “climate is what you expect to get and weather is what you actually get”, he believes that to gauge the climate you need a thirty-year weather sample. In recent years, he says, he has recorded higher temperatures, heavier rainfall and an increase in extreme weather events.   

physiological effects

In 2018 Harley published the book The Psychology of Weather, an exploration of how the weather we experience can influence everything, from what we buy to the way we think about life and death. To find out more, Speak Up contacted Harley. We began by asking him to what extent we are at the mercy of the elements. 

Trevor Harley (English accent): The weather affects us in many ways, both physiologically and psychologically. I think the physiological ones are obvious: when it gets too hot, people suffer from heat stroke, heat stress. We had a heatwave this summer in the UK, and the death rate climbed quite dramatically. Similarly, obviously, in cold winters, snow — people suffer from hypothermia. They can’t afford heating in particular. They tend to fall and slip on ice and break limbs. But it is the psychological effects I’m most interested in. And virtually every type of weather has a particular psychological characteristic, corresponding thing that goes with it.


So, are people usually happier when the sun shines

Trevor Harley: When it’s sunny, we tend to be in a better mood. Now, that isn’t always the case, because, believe it or not, there are a significant proportion of people who actually don’t like the sunshine. It’s hard to believe but it’s true. But sunshine is good for us: it raises our mood; it has an effect on the chemical serotonin, which is a neurotransmitter in the brain and the drug which is affected by the SSRI anti-depressants. Sunshine also stimulates the pineal gland, which is a small gland at the base of the brain, which produces a hormone called melatonin. Melatonin is involved in regulating our sleep-wake cycle. When that goes wrong, as it does with seasonal affective disorder, it affects our mood, people become prone to depression. And that’s why lack of sunshine in winter can cause quite severe depression. I’m a bit prone to it myself. So sunshine has all sorts of effects. It even lowers blood pressure. It’s a good thing. It stimulates vitamin D production, which affects the immune system, and also affects mood. Of course there is the caveat that sunshine obviously increases the possibility of skin cancer. But, if people are careful — just use common sense, avoid going out in the sun when it’s extremely hot or high in the sky — sunshine in the right amount is pretty essential.


However, heat such as that which struck Britain last summer can affect us negatively, says Harley.

Trevor Harley: Heat affects us in various ways too. It increases the probability of people being violent. If you look at the distribution of riots across the world, they tend to happen on hot summer nights. There are lots of possible reasons. Obviously when it’s hot, people tend to drink more alcohol, but lab experiments have shown that just increasing the temperature makes us angrier. So hot weather tends to make people angry and that leads to rioting. And also the rate of violent crime goes up. The hotter it is, the more likely violent crimes such as murder, robbery, rape, assault… that rate increases, too. However, once it gets to a certain point, it can be too hot, and essentially then people are just too hot to be able to do anything. They just sit around, sweating and complaining.


The British are famous for obsessing about the weather. We asked Harley if climate can influence the personality of the people living in a country.

Trevor Harley: In terms of national characteristics there has been some research looking at how climate affects personality, and it is really what you would expect from popular belief: the idea of people being more hot-blooded as you approach the equator. Well, as I said earlier, the hotter it is, the angrier people get, more passionate, more romantic. Whereas the nearer we get to the poles, the more staid, reserved they tend to be. Now Britain tends towards the reserved, quiet personality type. And I think that is in part due to the weather. 


Not only can the weather shape our personality, it can also affect the economic development of a country. 

Trevor Harley: I think also the weather here has had a big effect on history because it’s wet, and that gave rise to plenty of water and that enabled the Industrial Revolution, with waterpowerwater mills and so on, ready access to water for smelting... So I think it’s had a big effect on our national psyche, but also on our history.


Harley is not a fan of strong wind. He does, however, have an interesting theory as to why people in the past might have appreciated it. 

Trevor Harley: Wind is actually my least favourite sort of weather, and when I’m out walking Beau, my dog, I can bear most things — heavy rain I don’t care, but wind I really dislike. It is true that there are circumstances in which people welcome a bit of wind — a sea breeze, if it’s very hot. But that doesn’t happen very often. Wind used also to have the advantage of lifting fog. And in particular in Britain in the forties and fifties was very prone to smog in big cities, a combination of smoke and fog. And that happened when there were big areas of high pressure over us without much wind. The wind would lift it and clear the smog. So my mother liked a good breeze, “a good blow”, as she said, because she thought it was good for the lungs. But now, we don’t get smog since the Clean Air Act, and I think that most people aren’t that keen on it any more. Generally now we have more extreme weather events, people are a bit more worried about weather disruption and what severe storms can do to infrastructure.

Everyday Dialogues: Talking About the Weather