Andy Burnham will chair an emergency Cobra meeting in response to extreme heat, which has caused wildfires and plunged many parts of Britain into drought.

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

A No 10 spokesperson said the government understood firefighters, farmers and NHS staff were all facing challenges connected to the weather. Ministers from the Department for Environment, Food and Rural Affairs (Defra), the Home Office and Department of Health and Social Care, as well as officials from the Environment Agency, will attend.

It will be the second Cobra meeting this year on heatwaves, after one took place amid high temperatures in June. It comes as parts of the country face their fifth heatwave this summer and the number of days reaching 30C in any year in the UK hits a new record, with 35 days so far beating the 34 days set in 1995, according to the Met Office.

The climate breakdown has been linked to the increasing frequency of wildfires, burning larger areas, across many parts of the world. The “fire wave” under way in the UK is the most widespread the country has ever experienced, with the combination of wet winters and prolonged heatwaves exacerbating the risk.

A No 10 spokesperson 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.”

Rare amber “extreme heat” warnings have been issued 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.

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, the general secretary of the Fire Brigades Union (FBU), warned the country faced an “unprecedented summer of dangerous and volatile wildfires”. The National Fire Chiefs Council said firefighters have responded to more than 950 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 more than 450 incidents.

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 droughts develop very quickly because of a combination of very low rainfall and high temperatures.

The FBU warned that in many parts of the country, firefighters do not have the latest equipment to deal with these.

“They do not have the new modern personal protective equipment, the lightweight fire kit that we wear, the right helmets, lightweight helmets, breathable uniforms to make sure they’re better protected, their health is protected when they’re out dealing with these incidents for hours and hours on end,” Wright told Times Radio.

The government said it had announced £97m in new funding to upgrade national firefighting capabilities, including off-road vehicles and specialist equipment.