The recent hot weather can be very bad for computers, in particular the hard disk drives contained in them. Although many companies have air-conditioning, there are an alarming number who do not and when the outside temperature rises, an office containing one or more computers can become excessively hot. At home very few people have air-conditioning, meaning that most home computers will also suffer from high temperatures.
Even by using portable fans, it will have no real effect on the temperature, especially the air inside a computer case which will become extremely hot. Even with internal fans blowing air across the hard disk, the cooling effect will be significantly reduced meaning that the drive will be operating at an excessively high temperature, which is likely to cause damage, which may only become apparent at a later time.
It is also common without air-conditioning to open a window, usually in an attempt to allow air to flow into the room. It is important to remember when the temperature in the UK rises, the chances of a thunderstorm occurring later in the day or even overnight are high. Never leave any window open unattended through which rain could enter the room, if your computer is also installed close to it, as it fairly common.