Unfortunately, the stereotype of London as a rainy city turns out to be completely accurate. It does, in fact, rain at least once a day, and the days it doesn't rain are usually cloudy throughout. If you come from a place with a good climate, then the weather in London will surely be a shock, and you are likely to be horribly depressed about it. If weather is not that important to you then, well, it doesn't matter. The sunny days are, therefore, treasured like a precious gift by most of the students.
There are redeeming qualities to the weather in London. In the winter, the temperature rarely reaches below zero, so, therefore, it does not snow all that often. Freezing rain, on the other hand, is common. Spring also comes early in England, so the winter is hardly felt. The problem is that when the weather turns nice in the springtime, students are in the middle of their exam period and have very little time to actually enjoy it. There is a reason why the British always vacation in the sunniest places in the world.