Rainy days in Roussillon area suggestions

Depending on where you are and what you like, Ceret has a magnificent art museum.
http://www.musee-ceret.com/mam/index.php

I'm traveling and don't have access to my notes from last year's trip to France, but:

• Avignon has the Palais des Papes (basically unfurnished; I liked it but many people don't) and at least one art museum.

• Arles has a modern archaeological museum.

• Antibes has at least one art museum.

Nice is the mother lode of art museums, but I don't think you'd want to drive that far. Marseilles is closer, but I didn't like the Marseilles museums as well.

In my experience, precipitation predictions are very unreliable. It may not be nearly as bad as you're expecting. If you're looking more than 2 or 3 days out, I'd try to forget about the weather temporarily. I look at the next day's forecast, but often when I get up the next morning, it has changed. And of course what actually materializes may be different.

There are many wineries that offer tasting in the Languedoc-Roussillon region. As mentioned above, though, rain seldom lasts long, so I wouldn't let it keep me from doing whatever I have planned. Maybe that's just my Seattle attitude where if we let a little rain stop us, we'll never do anything.

Thanks for your suggestions, and as to the forecasts, they are turning out to be spot-on this time! Even the locals are complaining about the awful spring they have been having!
Are there any other galleries in Avignon besides the Palaise du Popes?

Yes, very nearby. Sorry I don't remember the name of it; I'm in Hungary at the moment. You can check TripAdvisor's Things To Do list if you don't have a guidebook.