London Marathon weather – a more detailed look

It’s that time of year again when tens of thousands of people will be digging out their running shoes and lining up to take part in this year’s London Marathon.

Whether running professionally or for a good cause, the event brings thousands of spectators to the 26 mile course to cheer runners along and one thing that will be on everyone’s mind is the weather.

I’ve already had lots of people sending me tweets asking what the weather will be like on Sunday, so I thought it would be helpful to have more of a detailed look at what to expect.

First of all, however, I thought it would be interesting to look back at past London marathons and see how varied the weather has been from year to year.

April of course is a month that can produce a huge range of weather conditions, so it’s rare that any two years will deliver exactly the same type of weather.

Past marathon weather

April being such a fickle month has provided a big range of temperatures since the marathon’s inception in 1981.

The hottest marathon days were on 21 April 1996 and 22 April 2007 when the temperature reached a summer-like 22.2C which would have been challenging for the runners.

At the other end of the spectrum, the coldest marathon day was 18 April 2004 when the temperature got no higher than 5.3C, more akin to mid-winter.

The wettest marathon day on record was also on 18 April 2004, when the cloud and rain no doubt played a notable part in suppressing the temperature.

Statistically the average amount of rain falling on marathon day is just 1.3mm over 30 years and the average amount of sunshine 5.8 hours.

This year’s marathon weather

The weather this year is looking typically April-like, with the elements not looking extreme in any sense. Nevertheless, I’ll break it down into the chance of rain, temperature, humidity and wind.

Chance of rain is likely to vary as the race goes on – especially with Sunday being another sunshine and showers day. From 7-10am for the start line, there’s a good chance that it will be dry with sunny spells. However, after 10am cloud will develop with an increasing risk of showers towards midday, some of which could be heavy in the afternoon.

Temperatures at 9am will be around 8C, so it will feel quite cold waiting around at the start line – certainly worth taking a few layers to keep warm prior to setting off. The temperature will then rise to around 13C by midday, so great for running, but dropping back to 8C in any showers.

Humidity is expected to be around 60% for the race, so it’s not expected to feel humid at all. This is good news because it means that the air still has plenty of capacity to allow sweat to evaporate from runners, ensuring that the body’s natural cooling mechanism can function well.

Wind is expected to be light to moderate and from a west to south westerly direction, so for the westerly facing parts of the course, there will be a slight head wind. But on the positive side, the breeze will keep runners cool, although if you’re standing still as a spectator, you may feel quite chilly.

So, that’s how things are looking at the moment, but you can always get the latest 3 hourly forecast for London here.

Good luck if you’re taking part and if there looks to be a significant change in the marathon forecast, I’ll post updates on Twitter – @liamdutton

Historical marathon weather data courtesy of the Met Office