The prime minister will chair a meeting of the Cobra emergency committee on Wednesday in response to extreme heat, which has caused wildfires and plunged many parts of Britain into drought.

Andy Burnham will meet with ministers, officials and agencies as high temperatures continue across the UK on Wednesday afternoon, with temperatures of 33C forecast, and up to 38C on Thursday.

It will be the second Cobra meeting this year on heatwaves, after one took place amid high temperatures in June. Ministers from Defra, the home office, the health department and officials from the Environment Agency will be present.

A Downing Street spokesperson said the government understood firefighters, farmers and NHS staff were all facing challenges connected to the weather.

The Met Office has said the UK is on course for its hottest summer on record, as parts of the country face their fifth heatwave this summer.

Rare amber “extreme heat” warnings have been issued by the forecaster for London and parts of the south-east, East Midlands, east of England, West Midlands and South Yorkshire from 9am to midnight on Thursday.

The government urged the public to pay attention to UK health security agency heat alerts and advised people to drink plenty of fluids and check in on family, friends and neighbours who may be at high risk.

A No 10 statement said: “The prime minister will chair a meeting of COBR – the government emergency committee – this afternoon on the UK’s ongoing response to extreme heat, wildfires and drought.

“We know how challenging this summer is proving, particularly for firefighters tackling wildfires, farmers working in drought conditions, and NHS staff in busy A+E units.

“We will continue to take the action needed to keep communities safe, protect water supplies and safeguard the environment.”

The Met Office chief forecaster, Chris Bulmer, said: “While the peak heat will be more short-lived than recent heatwaves, temperatures widely into the mid-30s Celsius on Thursday brings the potential for impacts for some, which is why a Met Office warning has been issued.

“High pressure is now becoming dominant and temperatures will build day-by-day. Southerly and south-easterly winds will also tap into the hot conditions over Europe which helps develop this further notable heat in what has been a hot and dry summer so far for many in the south of the UK.”

On Tuesday, Steve Wright, general secretary of the Fire Brigades Union (FBU), warned the country faces a “national emergency” because of the wildfires. Firefighters have responded to 966 wildfires across England and Wales this year, including 185 in the first 10 days of August alone, while July was the busiest month on record for wildfires with 458 incidents, the National Fire Chiefs Council said.

Nearly three-quarters of England and the whole of Wales are in drought, after a record dry July and very dry start to August has combined with high temperatures to put pressure on water resources.

Southern Water has applied for a rare non-domestic drought order which would ban businesses from non-essential water use, including cleaning cars and filling swimming pools, saying an “exceptional” lack of rain has threatened supplies in Hampshire and the Isle of Wight. It warned that 165,000 people in the Southampton West supply area could face restricted supplies. The environment secretary, Angela Eagle, will decide on the application, which would be the first such ban since May 2006.

The Environment Agency said 71.3% of England is now experiencing “flash drought”, as a dry start to August followed the country’s driest July on record. Flash drought is one that develops very quickly because of a combination of very low rainfall and high temperatures.