PARIS — Firefighters in France and Spain raced to contain huge wildfires on Tuesday before another surge in temperatures threatens to worsen conditions.Temperatures are set to soar in France and Spain this week as the continent heads into its fourth heat wave of the summer, and there is no rain forecast to relieve the tinder-dry conditions fuelling the fires.More than 300,000 people have been forced to flee their homes in the two countries, in what the Associated Press described as one of Europe's largest evacuation operations in decades.In southwestern France, firefighters managed to prevent a blaze near Bordeaux from expanding overnight, although several flare-ups were reported. The fire has burned around 42,000 hectares over six days, forced 220,000 people to evacuate and destroyed 240 homes.President Emmanuel Macron warned that "the coming weeks will be tough and we have to hold out".“Intense heat waves are settling over a large part of the country, with a peak in intensity on Wednesday,” said France’s weather service Météo-France on Monday. Temperatures in Bordeaux, near France’s biggest blaze, are forecast to reach 104 degrees Fahrenheit (40 Celsius) on Wednesday.In Spain, “the heat wave will be long,” lasting at least until Sunday, according to the country’s national weather service AEMET. The risk of fires will rise to “extreme levels,” it added.The heat is likely to make already dangerous fire conditions much worse. France and Spain face “very extreme conditions” for fire until at least Wednesday, according to the European Forest Fires Information System.In Spain, firefighters are battling blazes west of Madrid which have forced around 60,000 people to evacuate. Interior Minister Fernando Grande-Marlaska said the coming hours would be "absolutely decisive" as temperatures begin rising again.Reacting to the forecast, Spanish Prime Minister Pedro Sanchez said: "I ask for understanding and call on all citizens in all the country to exercise extreme caution and take every possible precaution.""We face difficult hours, complex hours" ahead, he warned.The scale of the destruction has been particularly severe in the region, where around 77,000 hectares have been burned by the current fires — an area roughly the size of Hamburg.The European Union is using its Copernicus satellite system to monitor the fires and provide authorities with rapid mapping of affected areas, helping emergency services assess the spread and impact of blazes.The bloc's Civil Protection Mechanism provides aircraft and firefighters supplied by member states and the EU-funded rescEU reserve, but that capacity could face further pressure as another spell of extreme heat moves across Europe.Since the beginning of the year, around 150,000 hectares have burned in Spain and 115,000 hectares in France but EU Crisis Management Commissioner Hadja Lahbib has warned that the threat extends beyond the countries currently battling major fires.The EU has deployed additional water-bombing aircraft to France, but Lahbib warned that resources could soon be needed elsewhere."Extreme conditions are looming for Hungary, Slovakia and the Czech Republic, in addition to France, the Iberian Peninsula... where the situation is expected to worsen, including in Portugal starting today," Lahbib said.Western Europe has endured rolling, climate change-fueled extreme heat waves since May, sweltering under a succession of heat domes. These act like a lid on a pot, trapping hot air and turning the landscape tinder dry, priming it for the fires that are still raging in both countries.