It's hard to describe an average UK summer because this island country has huge variations in temperature, rainfall etc from one day to the next, and even from one hour to the next sometimes. Also, being a long thin country it has great differences between north and south especially. In parts of the southwest the UK so mild that palm trees flourish, whereas in parts of Scotand it is much colder, and even occasionally has some snow in summer.
Generally, the Uk has a fair amount of rain even in the summer (the east coast of England is the driest part). Temperatures have been recorded of over 36 degrees (the highest ever is 38.5) but generally anything over 32 is unusual. In fact the overall average summer temperature for the whole of the British Isles is around 15 degrees celsius, but most places can expect daytime temperatures of anything from 20 to 26 as normal.
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