Britain's record-breaking dry spell is set to be interrupted by heavy downfalls this weekend, with thunderstorms potentially bringing some reprieve to firefighters tacking heathland fires.

Despite temperatures staying warm and humid, heavy and thundery showers are expected in most areas of the UK by Sunday, weather experts said, with up to 25mm of rain in localised areas.

Gemma Plumb, a forecaster at MeteoGroup, the weather division of the Press Association, said: "Today we will see pulses of showers and thunderstorms moving up from the south during the day.

"Almost all areas will see some sort of rain with the exception of East Anglia and parts of Kent. There will be very heavy showers in parts with some places getting high rainfall totals of between 20mm and 25mm."

The hottest April on record, which saw only a fifth of the expected rainfall in England and Wales, has caused vast areas of parched, tinder-dry land to go up in flames over the past week. Temperatures of 20C or more are expected in many parts of the country over the weekend.

It is hoped the predicted storms, triggered by warm air moving up from Spain, could aid the emergency services and with more rain expected on Sunday the fires could be finally quelled.

Ms Plumb added: "There will be heavy and persistent rain moving up from the south overnight and that will reach all areas, apart from the far north of Scotland and eastern part of East Anglia, by Sunday morning."

This is likely to prove welcome to Royal Berkshire Fire and Rescue Service, which is still tackling heathland fires in the Swinley Forest area.

"Water has been pumped at high volume from 30 fire engines there as crews continue their round-the-clock efforts to extinguish it. Police have bailed two 14-year-old youths arrested on suspicion of arson.

Firefighters are still hosing down burning moorlands in Lancashire, with blazes raging on more than a six square-mile area at Belmont.

Seven appliances from Greater Manchester Fire and Rescue Service were sent to tackle an ongoing blaze at Turton, while two teenagers were arrested on suspicion of arson after a large moorland fire near Halifax.

Crews in Northern Ireland have fought more than 1,000 gorse and forest fires in the past four days in what chiefs said was the busiest time in 30 years. Around 200 personnel, including soldiers, have battled 255 fires in 31 locations since Tuesday, according to the province's deputy chief fire officer Chris Kerr.

In the Scottish Highlands, wildfires broke out in Inverkirkaig, Lochailort and in Newton of Ardtoe in Salen, while the National Trust for Scotland said at least £100,000 of damage had been caused to its forest regeneration project in Torridon and Kintail.