The warning is in effect from 1pm to 9pm tomorrow, with heavy showers expected to accompany the storms across central, southern and eastern England. The forecaster says that while only a small amount of rain will fall in most places, there is a chance of some isolated heavy downpours and lightning. In these specific cases, in some areas 20 to 30 mm of rain can fall in one hour, up to 50 mm in three hours. The rain will be a breath of fresh air for many protecting themselves from the scorching 40C heat today.
A total of 36 regions and local authorities are covered by this latest alert, which covers parts of Kent, Sussex, West Berkshire, central London and extends from Peterborough to Nottingham.
In terms of what to expect, the Met Office warns of public transit delays and cancellations due to flooding or possible lightning strikes.
Splashing water or flash flooding can also lead to difficult driving conditions and some road closures.
And there is a small chance of power outages that could affect homes and businesses.
The new warning will be implemented just over 12 hours after the red extreme heat warning has expired.
Much of the country is currently sweltering in heat of up to 38C, with some places likely to hit a record 40C.
People are being warned to avoid travel and stay hydrated as this unusual weather grips much of the UK.
Just before 10am, Kew Gardens in southwest London was the hottest spot in the country with a temperature of 35.1°C, closely followed by Heathrow Airport at 34.5°C.
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As part of the Met Office’s safety advice for storms, it says people should stay indoors if lightning strikes and avoid the sheltered side of boundary walls and fences.
It says that if these structures fail, they will collapse on this side.
For those who drive, it urges people to stay on the main roads and avoid small country roads where flooding or even fallen debris could lie.
Thursday, Friday, Saturday and Sunday are currently free of warnings.