We are all aware that the weather influences our mood. In fact, most of us are affected in some way with the arrival of the heat, or the rainy days, sunny days or grey days, for example. But, how does this really impact?

In a 2008 study published in the journal Emotion, the researchers evaluated the personalities and moods of more than 1,200 adult men and women through questionnaires daily. By analysing the results, they found that the climate-related factors, such as temperature, sunlight, wind and rainfall did not have a noticeable impact on the positive mood, but the temperature, the wind and the light of the sun itself had an effect on negative mood

The study looked at the effects of the weather on affect – mood – and levels of tiredness. Participants kept a diary tracking these variables. The results showed that the principal meteorological variables that affect us are the temperature, wind, and amount of sunlight. 

Low mood was related to temperature, the amount of sunshine, and the strength of the wind; 

Tiredness was related to sunshine. There were also effects of whether it was raining and of atmospheric pressure, but the sophisticated statistical analysis showed that these were primarily due to the amount of sunshine

Sunlight is our main source of synthesizing vitamin D which is critical in producing serotonin (the neurotransmitter responsible for regulating and elevating our mood). 

Low levels of serotonin have been linked to depression and in fact there's a very real psychology disorder called seasonal affective disorder which is primarily experienced in the darkness of winter

However, the effects of weather on mood are not straightforwardly biological. They are also psychological and social. 

One reason why heat is associated with aggression is that people interact more in public in hot weather. 

Indeed, the effects of weather on mood depend on our behaviour and on how we think. Most basically, weather will only influence us if we expose ourselves to it.