Scotland will continue to enjoy something of a heatwave but traditional April showers are also on the way, forecasters warned yesterday.

They said that this month was on course to become one of the warmest and driest Aprils since records began in 1914.

However, despite soaring temperatures clouds will move in bringing rain today and tomorrow north of the border. This contrasts with the picture in the south of England, where thousands of runners preparing to take part in tomorrow's London Marathon will have to cope with temperatures of up to 23C.

John Hammond, spokesman for the Met Office, said the outlook was not so pleasant in Scotland.

He said: "It will become a bit more changeable and unsettled. It won't be raining all the time but it will be different from what we have had recently. Temperatures are still looking above average because despite becoming more unsettled the wind is going to be relatively mild.

"The greatest risk over the weekend is tomorrow and it will be western areas as ever that see the highest rainfall. When it clears and the clouds break we could see temperatures as high as 16C, which is very respectable for April."

Around 35,000 runners are predicted to take to the starting line of the Flora London Marathon.

Temperatures are expected to reach 16C by 9am, peaking at 23C by afternoon.

Experts are warning of the risks of sunstroke and dehydration for those taking part in the annual race.

Scottish athlete Liz McColgan, former winner and world 10,000 metres champion, is running the last race of her career tomorrow, for Leukemia Research.

She said it was important that runners factored in the conditions in their preparation.

"The forecast conditions will make it very tough, especially for the ill prepared," she said.

"Elite runners know how to cope, and how to retain water. Too much plain water just depletes you.

"They have their own drinks prepared, diluted with fruit juice and perhaps some salt, so the body retains it - things Joe Public is unlikely to be aware of.

"Be well hydrated over the preceding days. Sip water before you start.

"Don't gulp it down at feeding stations. Sip it. I'd always carry a bottle for at least half a mile."

Organisers say they are well prepared for the heat and will have 800,000 bottles of water, enough to fill 12 Olympic swimming pools, on site for runners.

A spokeswoman for the London Marathon said: "We give our runners an enormous amount of advice on how to handle warm weather.

"We provide lots of water at stations all the way along the course, and we have showers in six or seven places for runners to cool off."