It ain't always great weather, and what's your definition of it?
But it can be very good to not have blue skies, and you're forced to work with greys.
I most often wait for or look for a spark of light, light effect or something that can be the backbone (idea) for the painting.
Once you have the idea you can create it, even if the circumstances change from it disappearing to appearing, continuously.
SSP02-2019 Seascape Plein air Painting 'Rain and Storm'
↪ Do not wait for the perfect day to paint. Just drive towards your subject, start looking around.
Most of the times there's something of beauty catching your eye, no matter what the weather or season is!
Just bring the umbrella + duct tape and you are fine painting outdoors.
This is a beautiful image, yes? It's my leftover paints in a box.
↪ It's easier to mix greys and it's faster when you have (leftover) mixtures to start from.