'Perfect' running conditions forecast for London Marathon day

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The good news for the 50,000 plus taking part is that temperatures will not exceed 19C at any point, and will be much cooler than the 22C felt last year.

The 26.2 mile event will begin on Sunday, April 26, from 8.50am for elite wheelchair races, from 9.05am for elite women, and from 9.35 for the elite men and masses - with waves being started through to 11.30am.

It means that racing will be continuing into the early afternoon, with the final finishers not crossing the line until around 3pm, when the weather might be warming up - but thankfully for most it is not set to be too warm to run.

"Low cloud and fog patches in the east will again clear by mid-morning," the Met Office said. "[It will be] a dry day with sunny spells then follows, although cloudier in the northeast. Feeling warm for most."

The marathon begins in Blackheath and finishes at the Mall, next to Buckingham Palace in central London.

London weather forecast for the day of the marathon

Sunday will be a sunny and clear day in London, with a chance of rain at less than 5%.

The temperatures forecast by the Met Office are:

• 11C at 9am,
• 12C at 10am,
• 14C at 11am,
• 15C at midday,
• 17C at 1pm,
• 18C at 2pm,
• 19C at 3pm

The maximum temperature of 19C will continue until around 5pm, when the heat recedes.

The average finishing time for a marathon is 4 hours 30 minutes, which means that it will be around 17C when this runner crosses the line.

This is ideal for running and might help the elite course towards a course, or perhaps even world, record attempt - with a Runners World study finding 2-13C is the optimum for running a marathon.

With the elite fields expected to come down the Mall from 11am, when it is 14C, this is not bad at all - and far more accommodating than the infamous 28C felt in the record heat of the 2018 London Marathon.

What is the pollen count?

While the weather is mild, the pollen count for Sunday has been forecast to be high - according to the Met Office.

"Pollen can cause significant irritation and inflammation in people who are allergic to it," the weather agency states.

There are many kinds of pollen which are more prevalent at various times of the year, and this weekend it is oak pollen that is set to be high in London.

Runners who suffer with the allergy can prepare by shutting windows the night before while sleeping, taking an antihistamine tablet, and using Vaseline to protect nostrils.