Tens of thousands of people taking part in the 39th London Marathon are expected to have favourable weather for running and racing through the capital.
Temperatures are expected to peak at around 16C (61F) on Sunday afternoon, while rain will be limited to a passing light shower or two and winds will be breezy at most.
Air pollution, the pollen count and ultraviolet (UV) levels are forecast to be low to moderate.
The first race, the Elite Wheelchair, is due to begin at 9.05am, while the main race is scheduled to begin at 10.10am.
Met Office meteorologist Alex Burhill said there will be a chilly start for everyone gathering in Greenwich, although temperatures will climb into the teens.
“It will be a little bit cloudy at first, but things should brighten up as we go through the morning and into the afternoon with some sunny spells developing,” he told the Press Association.
“There’s a chance of the odd shower, but it will be just one or two light showers nothing more than that.
“It’s going to be less windy than yesterday; it will be a bit breezy, but we are only talking gusts of 15-20mph so nothing especially strong.
“Temperatures will be around 8C (46F) to 9C (48F) when people are starting, but by early afternoon we are looking at highs of 15C (59F) or 16C (61F).
“Last year it was very warm and sunny which isn’t ideal, while yesterday it was a lot windier with some heavy rain around which wasn’t great, so in comparison to those days it’s much better for running.”
UV levels are likely to peak in London at level three on the index, which is classed as moderate.
Pollen levels will be moderate, while the air quality index is due to be level three, which means air pollution is low. Level four is moderate.
The 2018 London Marathon was hottest on record, with temperatures reaching 23.2C (73.8F) in central London.