Fancy-dress wearers have been warned to dress appropriately for Sunday's London Marathon with the race expected to be the warmest on record.
The forecast is for sunshine and 23 degrees Celsius (73.4 degrees Fahrenheit), which is set to beat the previous high of 22.2 C in 2007, leading event organisers to issue warnings to all participants to prepare for the conditions accordingly.
Race director Hugh Brasher said: "We have numerous contingencies and we continue to monitor the weather. It is Britain and weather is ever-changing.
"We are sending detailed information to all runners on how to prepare accordingly."
Brasher continued: "We have put extra water on the course to enable runners to douse themselves over the head and the back of the neck, we have added showers on the route and ice at the medical stations throughout the course.
"Anyone wearing fancy-dress, look at whether it's appropriate in the conditions. If you think it's not appropriate, don't do it in fancy-dress.
"People are urged to wear sun-screen and appropriate clothing. Listen to your body. Change your race plan."
Information from Press Association Sport was used in this report.