According to the Sunday Times, today is Saint Gervais in France, which is the equivalent of Britain’s Saint Swithin (July 15), which helps predict the weather for pretty much the whole of the summer:

St Swithin’s Day, if it does rain

Full forty days, it will remain

St Swithin’s Day, if it be fair

For forty days, t’will rain no more.

Unfortunately, today isn’t St Gervais in France, it is St Arsène, and this saint didn’t seem particularly interested in weather forecast. There is a similar saying in France, but it is linked to Saint Médard:

S’il pleut à la Saint-Médard (8 juin),

Il pleut quarante jours plus tard,

À moins que Saint-Barnabé (11 juin),

Ne vienne l’arrêter

Saint-Gervais (19 juin), quand il est beau,

Tire Médard et Barnabé de l’eau

If it rains on the St Médard (8 June),

It will rain for forty days,

Unless Saint Barnabé (11 June)

Stops it

Saint Gervais (19 June), when it is fair,

Drags Médard and Barnabé out of the water

Other countries have their own equivalents: Siebenschläfer in Germany (June 27), St Godelieve in Belgium (July 27) and St Henricus in the Netherlands (July 15). Of course, these dates are taken from the same article, so I’m not particularly enclined to believe any of it, could Belgian/German/Dutch readers confirm?
The article also indicates that there might be some scientific truth in the sayings, something to do with weather patterns becoming stable towards the middle of July, but how could this be, with all these neighbouring countries all having different dates for the beginning of a 40-day dry spell or deluge?
When I first moved here, it was one of those little things you have to get used to when you live in a different culture from yours. I used to miss it a tiny little bit on October 21, which is Sainte Céline. In catholic France, people would know about it and wish you "bonne fête"; you’d even get more people wishing you "bonne fête" than "bon anniversaire", as people are more likely to know your "fête" (it’s mentioned on the news) than your birthday (as long as they know your name). These days, I don’t even remember my own "fête", let alone anyone else’s. I’ll have to remember to mention this on my British citizenship application.