LONDON — London Marathon runners have been urged to reconsider dressing up in fancy costumes because Sunday's race is set to be the warmest on record.

Forecasts indicate sunshine and a temperature of 23 degrees Celsius (74 F), beating the previous high of 22.2 in 2007.

Extra water, ice, showers and medical stations will be available to runners throughout the 26.2-mile (42.2-kilometer) 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," race director Hugh Brasher said Thursday. "People are urged to wear sunscreen and appropriate clothing. Listen to your body. Change your race plan."