Let the weather change the route before it cancels the whole possibility.

Bad weather usually gets treated as a verdict on the whole plan rather than a constraint on one part of it. The walk becomes no walk, instead of a shorter walk somewhere sheltered. Cancelling is easier than adapting because adapting requires a second decision when you had already made the first one.

When the forecast turns, spend two minutes on the smaller version before you call it off. Indoors, closer, shorter, later: one of those usually works. Keeping the appointment in some form matters more than keeping it in the form you planned.