With moisture moving in from the Atlantic coast, national weather service Meteo France forecast light rain in the town of Lege-Cap Ferret, on a peninsula that has been a leading edge of the devastated region.
Local officials reported a "rather calm" night, with a fire that has not grown beyond the 42,000 hectares already affected.
Fire crews remained at "total mobilisation" with 2200 firefighters and more than 20 aircraft.
Rain fell early on Thursday in the city of Bordeaux to the east.
But there were no early signs of enough rainfall in the hardest-hit areas that could douse the flames or dampen the sandy ground and brushy undergrowth of pine forests that have fuelled the inferno.
Sophie Brocas, the prefect for the Gironde region, expressed some optimism that lower temperatures could help.
"If that's confirmed, we could foresee a return to a more normal life for residents, but also for businesses that need to work," she told reporters late on Wednesday.
Humidity reached 80 per cent overnight but was expected to drop by midday, authorities said.
Some rain was expected along the coast that "could reach the fire zone", Gironde officials said in a morning note.
Temperatures that peaked about 40C a day earlier were set to drop Thursday, topping out at 27C along the coast.
An "orange" heatwave alert - the second-highest level after "red" - was lifted shortly before dawn.
The fires in the Bordeaux wine-growing, forested and tourism-heavy region are among the blazes that have swept across pockets of southern Europe in recent weeks, including Spain and Greece.
On Thursday, firefighters were tackling multiple forest fires in four of Turkey's western provinces, the state-run Anadolu news agency reported.
Blazes in touristic Mugla and Antalya and elsewhere raged overnight as hot weather and strong winds gripped the region.
Residents were evacuated as teams with firefighting planes and helicopters battled the fires.
A day earlier, authorities in neighbouring Greece said three firefighters had died on the island on Crete, as the wildfire emergency stretched from the Atlantic coast to the eastern Mediterranean.
At the peak of the evacuations, a third of a million people were driven from homes and vacation sites in France and Spain.
