Science fiction novel where aliens give up invading Earth after experiencing severe weather in US (Tornado Alley/hurricanes?). I think I read it before 1990. Some small chance has Red Cross symbol on a structure’s roof on the cover.
It's a novella, not a novel, but this sounds fairly close to "The Gentle Earth" (1957) by Christopher Anvil.
I'll try to edit in some quotes later, but an alien invasion starts to go awry when they land in Tornado Alley. Quoting from a review on Goodreads:
A lengthy description of a Venusian military campaign unleashed against the USA.
Despite lengthy planning and a 50+ year technological advantage, the Venusians miscalculate both politically- their crude attempt to isolate the USA politically is a total failure- and militarily. They also never quite get to grips with Earth weather and environments