Found this on Tripadvisor.co.uk and I had to share it!
“An easy way to begin a discussion with a stranger (in a pub, queue, train, etc) is to talk about the weather. All British people have an opinion on the weather and most can tell you what the weather is due to do for the next 4/5 days. Being knowledgeable about the British weather is an essential part of living / visiting here. You will sometimes see people carrying umbrellas (brollies) on roasting hot, sunny days because they know that it will rain intensely later in the afternoon for about 45 minutes. You ignore this expert knowledge at your own risk. Remember – in Britain, there is no such thing as bad weather: there are only the wrong clothes. Avoid this by checking the forecasts, a good website for a 5 day outlook”