London Marathon Weather Forecast: How To Handle Running In The Heatwave


Pictured: Marathon des Sables in the Sahara desert / what London Marathon runners are imagining this year’s race will be like

In news that will be absolutely no surprise to anyone familiar with the machinations of Sod’s Law, the Sunday of the London Marathon is set to be hot as heck. This comes after training through what felt like the longest winter ever.

Normally a little sunshine would be reason to celebrate, but when you have 42.2km to run the mercury rising to 20°C or more is unwelcome, especially when you haven’t prepared for running in the heat.

Currently the Met Office’s London weather forecast is showing nothing but sun for the race, with temperatures rising from 16°C at 10am when the race starts to a high of 22°C in mid-afternoon. It’s not Sahara hot, but it’s enough to knock a runner who’s trained exclusively in the cold off their stride.

So what can you do about it? Well, the first thing is to remember that the forecast might change before race day, potentially even drastically. The Big Half half marathon in London in early March was almost called off due to freezing conditions, only for the day itself to be pleasantly mild.

There are also a few steps you can take to ensure that the sudden heatwave doesn’t ruin your London Marathon. Here are some top tips for running in the heat from Jason Taylor, running coach with, and Merrell ambassador Dr Andrew Murray, who has won races in the Sahara and Gobi deserts.

Adjust your outfit

Normally we’d say use the clothes you’ve been wearing for your long runs, but if those have all been in single-digit temperatures (or worse), then you might need to make some late adjustments.

”After you make sure your clothing is both comfortable and appropriate for the heat, give it a quick road test on one or two easy runs of 20-30 minutes,” says Taylortes. It is very easy to dehydrate by wearing layers that are too warm. Also, ensure your clothes don’t chafe – use Vaseline if required.

“Looking at the forecast I would recommend a lightweight running cap for the day. As well as helping to shade your face, this will keep the worst of the heat away from your head.”

“I wear white or light-coloured loose-fitting clothing,” says Murray. “I will also wear sunscreen, and a buff around my wrist to wipe excess sweat away.”

Look after your feet

“As the temperature increases, your feet will sweat more,” says Taylor. “Make sure your socks fit well and are in good condition. If needs be, tape any hot spots or use blister protection such as Compeed.

“Always lace the running shoe from the bottom up so it is snug, but not so tight it feels like a tourniquet.”

Get acclimatised

Sunday isn’t going to be the hottest day of marathon week – Thursday and Friday look likely to be even warmer, which give you a good chance to get your body used to the heat.

“In the days leading up to the race, try to be outside in the heat of the day,” says Murray, “and spend some time in a hot bath if you are not used to running in hot conditions.”

Hydrate, hydrate, hydrate

The London Marathon has water stations at every mile marker and Lucozade Sport is also available at regular intervals. Take advantage and remember you don’t just need water – you need electrolytes too.

“If you are running without a bottle make sure you drink at every drinks station and use electrolytes pre-race,” says Taylor.

“Electrolytes are lost through sweat in significant amounts and must be replaced. Replacing electrolytes is essential to keep your body hydrated, enhance performance and help prevent muscle cramps.”

Lucozade Sport contains electrolytes and you can also take hydration tabs with you in a running belt and dissolve them in water on the course.

Look out for shady spots

Take advantage of the shade provided by London’s tall buildings, or just spend the whole race running in the shadow of a really tall person.

“Running in a group may stop some direct sunlight from hitting you,” says Murray, “and I also try to run on the shady side of the road if there is one.”