The best time to visit London is a tough question to answer because there is often abounding to see and do all times of the year. If you desire pleasant climate then the summer months June to September are your best bet, but the climate in the UK is never dependable so it’s best to be arranged for all weather. The summer months will be warmer in general but some summers are still very damp!
January is the month to visit if you desire to strike the stores as the sales will be in full sway and everyone will be going buying absurd. February and March can be a bit boring with reduced cloud and rainfall climate wise, but the melodies and theatre view will be rather good. With the coming of April, London celebrates kinds of festivals in full sway. Recent years have witnessed some warm weather in April and May but afresh this is not to be expected.
June and July is summer and can be moderately hot but raincoat on standby is advised. At the end of July and the first couple weeks of August sees London warm. After summer months September and October has seen good climate in the last couple of years. It can be usually moderately hot and dry. November and December could be chilly. Lots of fireworks displays and events will be going on though so there is plenty to see and do. The shops will be preparing for the Christmas rush. Commonly by the end of November all the shops are covered with Christmas adornments and are aiming at the Christmas shopper.
So, no matter when you visit, one thing is for sure that you will encounter new everything with every change in London weather.