Later on today there is a meteorology talk by multiple world record holder glider pilot Klaus Ohlmann, who lives and flies locally. Then at 5.30pm there is the official opening ceremony.
Wikipedia has a good page on the mistral:
The mistral in France is a cool or cold, often violent, and usually dry wind, blowing throughout the year but is most frequent in winter and spring. It blows from the northwest or north of Europe through the valley of the Rhône River to the Mediterranean
Organisers say what is blowing now is a 'petite mistral'. That is, it blows at 40 kmh, not 90 kmh.
It's not only a wind - it helps shape life in Provence. According to Wikipedia:
"The mistral plays an important part in the life and culture of Provence, The mas (farmhouse) traditionally faces south, with its back to the mistral. The bell towers of villages in Provence are often open iron frameworks, which allow the wind to pass through. The traditional Provençal Christmas crib often has a figure of a shepherd holding his hat, with his cloak blowing in the mistral."