The world’s largest marathon takes place in the UK this weekend. The London Marathon will be run for the 33rd time and is expected to attract at least 35,000 runners, despite security concerns following the explosions which took place at last weekend’s Boston Marathon.



Many of those runners will be raising funds for various charities. In fact, London is the largest annual fund-raising event in the world. Since its beginning in 1981, more than $670M have been donated to various charities.



Despite this, for the majority of runners the race is all about their finishing time. A ‘personal best’ is what many of the more experienced runners will be hoping for.



London is a mainly flat, and therefore relatively fast, course. At least four world records have been set here over the years. Yet, more often than not, fast times are dependent upon the one thing runners cannot predict: the weather.



Distance athletes usually prefer dry but cloudy weather conditions, although there is no evidence that cloud cover has a direct impact upon race times.



What is known is that low humidity and cool weather are associated with improved times. Research shows that performance peaks at temperatures between 10 and 13 Celsius for men, and 11 to 14 Celsius for women.



The latest forecasts suggest that conditions on Sunday will be as close to perfect as could be hoped for. It will be dry throughout the race with early sunshine turning hazy towards the latter stages of the event.



Temperatures on race day are expected to be near perfect for running. For most runners, race temperatures will be in the range of 10 to 13 Celsius.



Early morning temperatures may be as low as 3 to 4 Celsius so keeping muscles warmed up will be an issue.



So expect an exciting race and an amazing spectacle around the street of the UK capital on Sunday.