Unless they're in obvious distress, leave them alone. The ones who don't find brumation sites and don't survive the winter shouldn't be passing their genes to the next generation anyway. We water down the gene pool in captivity for our own benefit, but it would be detrimental to do it to a wild population.

Native species have survived for thousands of generations, many of which saw summers like this past one. Individuals may die, but the population will go on.