The call to prayer has been issued by Xavier Malle, the bishop of Gap, in south eastern France.
He was prompted to issue the unusual instruction to worshippers after receiving a letter from a resident of the village of Lautaret in the Hautes-Alpes department.
The worried member of the public pleaded with the bishop to pray for rain, because they hadn't had a drop in six months and the drought was taking its toll.
So from Friday until Sunday December 10th the Christians of the Hautes-Alpes have been asked to pray for rain.
And he's serious.
“There is a specific prayer mass to ask for rain which is not very well known but which exists in the priest's book,” he told France Info radio.
“Our department has experienced a terrible drought for the past six months. People speak of the beauty of our region and everyone is proud to talk about the 300 days of good weather each year, but in reality the situation is tragic for all of us,” he said.
(Rivers have been drying up in the French Alps. AFP)
The drought has had a particularly bad impact on farmers, but the bishop is concerned that it may lead to environmental hazards such as forest fires.
The bishop also hopes the three-day prayer-athon will help worshippers become more aware of man's role in climate change.
“We are responsible for climate change,” he said. “So this is not just a prayer but it can also raise our awareness to realise that water is sacred.”
The good news for the bishop is that prayers already appear to have been answered with rain forecast for the coming days.