Anywhere in the bottom half of France will have temperatures in the mid to high 20's, and possibly even higher. It used to be a standing joke in the family as to where we would hit the sun. Would it be Lyons or further south. However, over the last few years the western part of France has often been pretty wet and most people head for the Med to guarantee the sun. Also the Bay of Biscay can be foggy when an Atlantic Low blows in. We have had excellent holidays in the south west of France, but also others where we ended up travelling across to the Med to find the sun.
If you are travelling in July I am sure you are aware it is high season and the sites will be very busy especially in the good areas. I do not wish to sow the wrong seeds but we also have been to Majorca a lot and thoroughly enjoy it. However, in our opinion it is definitely not the same as France. Majorca has safe beaches, clean water and is a children's, and big kids like me, paaradise. France is also very good but beaches can be a bit 'hit or miss' and can be very windy in certain areas in Rousillon when the Tramontane blows. We often spend more time by the site pool than on the beach for the above reasons. However, France offers other attractions if sitting beside the beach, or pool gets boring.
We cheat nowadays and have one long holiday in France and then a 2 week break in Majorca so I can play with my green crocodile on the beach.