London Marathon spectators have been warned not to arrive in t-shirts and shorts as wet and windy weather are set to strike on Sunday.
The Met Office said conditions will remain damp and blustery throughout the day, which may suit the 30,000 joggers far more than those lining the 26.2 mile route.
Temperatures will peak at about 13C and downpours are expected to be quite heavy at times, especially later on.
The clouds will start to creep in on Saturday when this week's warm and dry weather should come to an end.
A spokeswoman for the Met Office said: "At the moment, it does look as though there will be rain and colder temperatures and blustery winds.
"There will be gusts of between 15 and 25mph depending on the time of day.
"The change could catch people out a little bit. It's probably not the best idea for spectators to turn up in t-shorts and shorts."
She added that the rain will be brought in by a weather system that is currently moving across the UK, so timings for showers remain fairly uncertain.
Last year's race enjoyed fine conditions with mostly blue skies and temperatures reaching 16C.
