The weather in May in the Loire region can include both sun and rain. Looking at the French weather web site, you'll see that the temperature is listed to be between 9°C and 18°C (48 - 64 Farenheit).
When we were there in 2003 it was warmer than that.
France has converted to using the Euro. Although you may still see prices in both Euros and Francs, only Euros can be used.
Visa card and Mastercard accepted in most places.
Don't bring $100 bills. Many banks will not exchange them as they are widely counterfeited.
From the US:
Dial: "011 33" then dial the French phone number. Don't dial an initial "0".
For example, to call the château dial: 011 33 2 47 45 16 31
Dial: "009 33" then dial the French phone number. Don't dial an initial "0".
For example, to call the château dial: 009 33 2 47 45 16 31