Well, right now there is extra hot weather, little wind, little installed solar power in France (and reduced solar power output because of the heat) and no problem at all either. There is a lot of spare gas capacity, the gas plants are mostly unused right now, and the nuclear plants are more than able to cope with the power demand, as less than 60% of installed capacity is needed now.

There is really no reason to think there is, or could be any problem in summer in the foreseeable future, since we are already in a worst case situation (highest temperatures ever recorded, basically no renewables used, nuclear as almost the only source of electricity at the moment) that is not problematic.