Even though it is virtually impossible to escape the crowds, March to May is probably the best time to visit London. Warm spring is a prime time for exploring blooming city parks and going wild and green during the St. Patrick's Day celebrations. High room and airfare rates reflect the surge of tourism from late May to early September. Besides excellent summer weather, the city enjoys numerous events like the Wimbledon tournaments, Notting Hill Carnival, and the Globe Theatre plays. You can always plan your trip for autumn and winter, but mind there is a higher probability that weather will pass you a curve-ball. Misty October will guide you through the London Film Festival and boozy nights in cosy pubs, while busy December will charm you with festive atmosphere. The main rule is, no matter when you visit London, pack an umbrella.