If France has a warmer winter climate, it must be sunnier. In truth, since Avignon has more cloudy winter days than we do, there is actually more winter sunshine in Maine. That raises an obvious question. Just because we are on the same latitude doesn't necessarily mean we have the same climate. The climate difference between southern France and mid-coastal Maine is caused by forces independent of latitude.
Different climates are a result of different air and ocean currents.
Whereas masses of cold arctic air moving south across Canada give the northern parts of the North American continent a mostly frozen winter, the situation in France is different. The Gulf Stream, a massive flow of warm water moving northward across the Atlantic Ocean from the Caribbean to Scandinavia, ensures that western Europe's winter will be mostly cool and moist. If judged on temperature alone, a gardener in Juneau should have a slightly easier time growing winter vegetables than a gardener in New York. But for winter vegetable crops, temperature is not the principal deciding factor. And that brings us back to latitude.