Wildfires raging across southern Europe have forced thousands to flee their homes and prompted officials to ban spectators from a stage of the Tour de France, amid warnings of “powder keg” conditions after a record-breaking early summer heatwave.

Hundreds of firefighters are tackling blazes that have burned through almost 20,000 hectares (49,500 acres) in Portugal, Spain, France and Greece. Strong winds are forecast to fan the flames and temperatures are expected to rise again this week.

In the remote foothills of the French Pyrenees near the Spanish border, 700 firefighters were struggling to contain an out-of-control wildfire that has ⁠scorched 5,000 hectares and prompted the evacuation of more than 10,000 people.

“This morning, conditions are ⁠deteriorating again,” said the French interior minister, Laurent Nuñez, on Monday, adding that with wildfires now blazing in five departments, twice as much land had burned in France so far this season compared with the same time last year.

The EU said on Monday it was sending ⁠four waterbombing aircraft to France from Cyprus and Sweden to help firefighters around the city of Perpignan. “Europe stands with France,” the European Commission president, Ursula ⁠von der Leyen, posted.

The Pyrenees fire has nearly tripled in size since Sunday. “It came within 300 metres [984ft] of the houses. We were shocked by how fast it spread, it was staggering – bordering on panic,” Patrice, from the village of Trévillach, told Agence France-Presse.

The blazes follow a premature May heatwave and another in June that shattered temperature records across western Europe, caused thousands of excess deaths and left vast areas of land particularly vulnerable to wildfires.

Chantal Mauchet, the prefect of the Hérault department, where several fires have burned through at least 300 hectares of land, said on Monday southern France’s wildfire season had “essentially started three or more weeks early”.

The World Weather Attribution group of scientists has said the extreme temperatures recorded in June would have been “virtually impossible” without the climate crisis. Temperatures are forecast to climb again this week, rising to 40C locally.

“Climate change is here, we are living the consequences and it is only the start of July,” said the fire chief for Pyrénées-Orientales, Eric Belgioino. “This season is going to be a long one for the soldiers fighting fires. You have to help us.”

The eastern Pyrenees prefect, Pierre Regnault de la Mothe, ordered Tour de France spectators “not to go near the route or to the finish area” of Monday’s third stage of the cycling race through the Pyrenees from Spain into France. He said it would be “limited to the passage of the riders only and vehicles essential to the race”.

On the Spanish ​side of the border, fire has ravaged 2,200 hectares, 97% of which has been in the protected natural area of Les Gavarres. The head of operations of the Catalan fire service, Eduard Martinez, said the blaze had a perimeter of 40km (25 miles).

Firefighters said their efforts would be complicated by rising temperatures and the many “smoking hotspots” within the perimeter, but announced late on Sunday that the blaze was stable and they hoped it would be extinguished ⁠during the week.

South ​of Catalonia, in ​Spain’s eastern Castellón province, more than 500 people were evacuated after a wildfire spread into the Sierra de Espadán national park.

In central Portugal’s Vouzela area, more than 1,200 firefighters supported by nearly 400 vehicles and 15 aircraft were trying to extinguish a blaze that broke out on Thursday and had burned across an area of 13,000 hectares by Sunday.

Spain and Italy sent firefighters and aircraft to help and emergency services said on Monday that while dangerous spots remained, 80% of the blaze was under control. Portugal’s interior minister, Luís Neves, described conditions as a “powder keg”.

Elsewhere, large fires also destroyed hundreds of hectares of forest, vineyards and scrub on the Croatian island of Hvar and at Tale in Albania, while in Greece, which was largely spared last month’s heatwave, flames set off by a forest fire tore through two factories in the northern city of Thessaloniki.

Greek authorities issued evacuation alerts for three suburbs and urged residents in parts of the city to stay indoors and shut their windows and doors because of toxic smoke from one of the factories, a recycling plant.

Another large wildfire broke out Sunday afternoon west of Athens, with 210 firefighters, supported by volunteers, specialised teams and 29 aircraft deployed to tackle the blaze burning through pine forest in the Mandra area.