"Viking weather", to describe when it's a bit rainy/snowy/drizzly out, but not enough to soak you unless you're out in it for an extended period, and not bad enough to freeze or chill you if you're active.
The kind of weather which would be unpleasant and discouraging to stand around in for hours as a sentry, but trivial to a raider, and therefore helpful to them. Which IIRC I probably got from a Bernard Cornwell novel.