The Loire Valley divides France in two, both geographically and climatically: to the north is the moist, temperate climate of northern Europe; southward lies the drier climate of the Mediterranean. July and August are peak months for tourism, but the weather then can be hot and sultry, and the top attractions can be packed. Moreover, water levels in Europe’s last great undammed river can drop, revealing unsightly sandbanks in midsummer. So the best time to arrive may be in the late spring, when the river still looks like a river and the châteaux gardens are beautifully blooming; or in the fall, when the crowds have thinned and the restaurant menus are showcasing the bounty of harvest and hunt. October is a particularly good off-season option—all is mist and mellow fruitfulness along the Loire and its tributaries.
On Sunday, when most shops are closed, try to avoid the main cities—Orléans, Tours, Angers.