UK, 2 July 2015
As forecast as early as last Thursday, the UK saw a period of record breaking hot weather yesterday (1 July 2015).
The warmest July day since records began and the hottest day since 2003, was recorded at Heathrow, when the temperature reached 36.7 °C at 3.13pm. The previous highest July temperature was 36.5 °C on 19 July 2006 in Wisley, Surrey.
A number of Met Office weather observation stations around the country recorded their all time maximum temperature.
As is traditional with hot weather in the UK it was accompanied by thunderstorms. Parts of the UK, especially in the North East, saw some impressive thunderstorms overnight with frequent lightning and hail the size of golf balls.
Over the 34 hour period to 10am this morning saw 19,525 lightning strikes, 15,273 of which were in Scotland.
Thunderstorms develop when the atmosphere is unstable - this is when warm air exists underneath much colder air. As the warm air rises it cools and condenses forming small droplets of water. If there is enough instability in the air, the updraft of warm air is rapid and the water vapour will quickly form a cumulonimbus cloud. Typically, these cumulonimbus clouds can form in under an hour.
As the warm air continues to rise, the water droplets combine to create larger droplets which freeze to form ice crystals. As result of circulating air in the clouds, water freezes on the surface of the droplet or crystal. Eventually the droplets become too heavy to be supported by the updraughts of air and they fall as hail.
What's in store for the next few days:
It will continue to be warm across the UK over the next few days, although it is unlikely we will see temperatures as high as yesterday. Southern England, central areas and South Wales should see temperatures in the mid to high 20s while further north we expect temperatures to be in the high teens to low 20s.
More thunder and lightning is expected during the rest of today and again on Friday night/ early Saturday morning. The expected intensity of the storms on Friday mean we have issued a Yellow 'be aware' severe weather warning.
Isolated heavy, and possibly severe, thunderstorms are expected to develop on Friday evening across parts of England and Wales. These are likely to become more frequent later and spread northwards towards southern Scotland. Some torrential downpours are possible leading to localised surface water flooding, with large hail and frequent lightning also possible hazards.