Andy Murray told to keep cool as mercury nears 100F at wilting Wimbledon

Wimbledon wilted under the scorching heat today with Andy Murray having to take extra precautions with Centre Court temperatures soaring close to 100 degrees Fahrenheit.

The British number one, who was hoping to win through to the quarter-finals against French opponent Richard Gasquet, was advised to drink more water than usual to stave off the threat of dehydration.

Spectators were being urged to wear sun hats and use sun block as the sizzling temperatures and baking sunshine replaced the downpours of the first week of the 125th Wimbledon tournament.

The Centre Court roof, used regularly last week to allow play to continue while the rest of play was suspended due to rain, was being edged in to protect Royal Box guests from the sun.

Officially the temperature was set to be around 90F (32.2C), but with 14,000 spectators packed around the Centre Court, it was expected to hit 100F (37.7C).

Free bottles of mineral water were handed out to fans queuing in large numbers outside the All England Club, and supporters were advised to drink as much water as possible.

Sports dietitian Linia Patel urged Murray to drink 50 per cent more water as he faced losing three or four litres of body fluid during his match.

"Once you become dehydrated performance is seriously impaired, usually in the form of a loss of concentration, sluggish movement and slower reaction times, all of which could cost him badly in a match," she said.

St John's Ambulance had 50 volunteers standing by with oxygen cylinders prepared to deal with fainting spectators and staff were on extra alert.

Even police sniffer dogs, who scour the All England Club, were given extra water supplies by their handlers concerned about the heat.

Clive James, training development manager at St John Ambulance, said: "Extreme heat can be dangerous, particularly for the very young and old, but by being prepared you can spot early warning signs of illness and care for someone who needs your help.

"Heat exhaustion and heat stroke are the most serious problems that can develop when the sun is out so it's essential that people can spot the signs, such as headache and dizziness, and get them out of the heat as soon as possible.

"Our advice is to wear sun protection, cover up and stay hydrated." The Wimbledon announcer told fans over the intercom as they poured through the gates: "It is definitely a day for hats, water and sun cream."

Teenager Nikhil Rai of Northwood said: "I have grown up watching Wimbledon on TV and they have mostly been played in the rain. This is my first time here and the sun is so hot. It is brilliant." But the heatwave - the hottest since 2006 - was expected to end abruptly with thunderstorms later in the day.

Netweather forecaster Paul Michaelwhite predicted "severe storms with large-sized hail, gusting winds to 70mph or more, torrential rain and even tornadoes". Met Office forecaster Byron Chalcraft said: "Thunderstorms are likely just about anywhere."