Heat waves are bad news for your brain and for all those sitting exams. Studies suggest that while the sun coming out to play can make you happier it also makes you ‘stupider’! Researchers have found that during hot spells candidates perform significantly less well in cognitive tests. In sharp contrast those who work and study in air-conditioned environments can hold together their mental abilities until the heat subsides. This backs up a recent study that found for every half-degree rise in temperature there is a 1% fall in learning.