I really wouldn't worry about frogs hopping about
when we get into this winter/spring/winter cycle.
This is part of their natural behavior. I would only
worry if your pond is such that the frog can not get
out once he got in, especially if he is of a species
that overwinter in leaf litter or under logs. Whenever
you 'change' nature that's when the critters get into
trouble. We don't like shorelines in our ponds as
it makes for a great heron buffet - many other critters need
them to enter and exit the pond.