The battle to contain a large wildfire spreading across the New Forest will go on for several days, experts have said, as wind changes and a desiccated landscape fuel the flames.

Smoke billowed above the deserted A31 road, the main tourist route into the New Forest national park where tens of thousands of families are on holiday, late on Tuesday while a helicopter flew above the blaze. Firefighters at the scene said they were trying to contain several hotspots across the more than 247 acres of dried heathland as winds swirled over the area.

One source at the scene said: “They are really worried that as they dampen down the top, the peat underneath is still alight and spreading the fire. It is too dry, too windy, and it is a real struggle.”

July was the busiest month on record for wildfires, the National Fire Chiefs Council said on Tuesday. Its services have responded to 966 wildfires this year, including 458 in July alone.

Parts of England are bracing for a fifth heatwave of the summer this week as climate breakdown makes extreme heat, drought and wildfires more likely. The Met Office said on Tuesday that the UK was on course for its hottest summer on record by average temperature. On Monday, authorities declared almost three-quarters of England officially in drought.

Hampshire fire and rescue service said it was facing many challenges, including maintaining a water supply and dealing with difficult terrain and changes in wind direction, but it was trying to mount a larger-scale attack on the blaze. Britain owns no dedicated water-bombing aircraft as used by fire crews in Europe.

“Thanks to the efforts of firefighters, we are managing to contain the fire,” it said. “We have been using a mix of fire engines and off-road vehicles to damp down and cool the edges of the area … to prevent spread and escalation. The police drone is being used to enable us to priorities hotspot areas and manage flare-ups.”

As the emergency services worked through the night, a spokesperson for the Fire Brigades Union said it was calling for the recruitment of 5,000 more firefighters to cope with the extreme climate conditions.

Firefighters have been at the scene since Sunday evening when a lorry caught fire on the A31 at Ringwood at around 5.21pm, sparking the blaze.

Each summer, millions of tourists camp, hike and cycle in the New Forest national park. This year the human-caused climate crisis, which is driving extreme heat, has turned the green English heartland of Hampshire – which has not had rain for 59 days – into a landscape more akin to Arizona in the US.

The A31 dual carriageway, which in August is normally nose to tail with tourist traffic, remained shut and ghostly empty on Tuesday with no timetable for when it would reopen. Along the abandoned route, two Shell petrol stations stood empty and closed outside the village of Burley.

A yellow high-pressure water pipe stretched 5 miles along the empty highway from a stream near the village to the blaze, where more than 120 firefighters from stations across the country continued to try to contain the burning.

Debbie Tann, the chief executive of Hampshire and Isle of Wight Wildlife Trust, said: “It is devastating. It is just dry tinder across the whole forest. It has spread really quickly because of these dry conditions. The New Forest is one of the most important habitats in Europe. It has so many rare species in the heathland – reptiles, adders, lizards, and then the birds like night jars. This is going to have a devastating impact.”

Sue Oatway, who lives in Burley, said people had come together to support the firefighters, many of whom are volunteers, collecting food and drink for them. On a community WhatsApp group, firefighters thanked the “amazing community” for the support.

Outside Oatway’s home, New Forest ponies sheltered from the heat under brown, dried-out trees amid withered bracken. Oatway said: “I have never seen it so dry here. Someone posted a world map today on a social media group. I knew about the wildfires in Canada and Europe, but the scale of them in the United States I didn’t know. They are everywhere, and now here on our doorstep.”

With the A31 closed, tourist traffic was forced on to back roads through the forest, causing jams on narrow lanes. Holidaymakers were continuing to try to enjoy their break but as the battle to contain the wildfire entered its fourth day, the reality of the threat was becoming clearer.

Jason Bunsell had been camping with a friend at Ashurst on Sunday night when the fire began. “We were coming back on our bikes and saw this big thick black cloud above, we thought it was a storm,” he said. “Then we got back to our campsite and my wife sent a message to me saying: ‘How far are you from the fires, are you all right?’”

Ian Buckman, a district lead volunteer for Arundel and Littlehampton Scouts, who was guiding 26 scouts and explorers on a cycle ride through the forest outside Burley, said: “I have never seen the forest so dry. The environmental impact is massive.”

Tourism is the largest single industry in the local economy. Within the national park boundaries, leisure and recreation trips account for £107.6m in income each year. But the threat of fire spreading and the impact of air pollution have prompted appeals for tourists to stay away.

Forestry England, which manages about half of the national park, said the operation to contain the fire could last for several days. Its spokesperson Esta Mion said: “We are very much asking people to stay away … it’s unpredictable. We just don’t know how long this incident could go on for. We’re certainly thinking it could be the next few days, for sure.”

Emma Howard Boyd, the chair of the independent National Heat Risk Commission and a professor in practice at the Grantham Research Institute on Climate Change and the Environment, said: “As the prime minister tours every region of the UK, it will be hard to miss the impacts of this extraordinary summer: wildfires, drought, parched farmland and people struggling to work in extreme heat. The government must now act with urgency to prepare the country for a hotter climate, cutting emissions while investing in the resilience of our homes, infrastructure, farms and public services.”