“Severe” thunderstorms and localised flooding may follow a heatwave across London and parts of the country, the Met Office has warned.

The weather service said thunderstorms today (Thursday) could feature “frequent lightning, torrential downpours and large hail”, as it issued weather warnings.

The Met Office said “many more locations” would meet its heatwave criteria following Wednesday’s warm weather.

However, some areas could see as much as a month’s rainfall in a few hours today which could cause flooding, the weather service warned.

A yellow thunderstorm warning is in place for London, Essex and much of the South East today from 1am until 11.59pm.

Here is the hour-by-hour for tomorrow (Thursday)

7am - Sunny intervals 19C

8am – Sunny intervals 20C

9am - Sunny intervals 21C

10am - Sunny intervals 22C

11am - Sunny intervals 24C

12pm - Sunny intervals 25C

1pm - Sunny intervals 26C

2pm - Sunny intervals 27C

3pm - Sunny intervals 28C

4pm - Light shower 28C

5pm – Heavy shower 28C

6pm - Light shower 27C

7pm - Sunny intervals 25C

8pm – Sunny intervals 25C

9pm – Partly cloudy 23C

10pm - Partly cloudy 22C

Here is the hour-by-hour forecast for tomorrow (Friday)

7am – Sunny intervals 19C

10am – Sunny intervals 22C

1pm – Sunny 26C

4pm – Sunny 28C

7pm – Sunny 28C

10pm – Clear 23C

Forecast in full

Thursday: A cloudy start with some showers, these gradually easing. Bright or sunny spells developing, before heavy showers and thunderstorms, possibly severe, develop into the afternoon. Hot and very humid. Maximum temperature 31 °C.

Outlook for Friday to Sunday: A fine start Friday before cloud and wind increases with a risk of showers. Rain clears east overnight leaving sunny spells and isolated showers Saturday. Turning cloudier and windy Sunday.

Met Office deputy chief forecaster Dan Holley said the most intense impacts on Thursday were “likely to be focused on central, southern and south east areas of England”.

He added: “Here some locations will witness torrential downpours, large hail and frequent lightning.

“A few places could see 50-100mm of rainfall in a few hours.”