When the night temperature is going to be under 13 deg. C. it is wise to cover the hutch or move it to a sheltered position.
If possible bring bunnies inside if the night temperature is forecast under 8deg. C
***In the wild rabbits would spend the cold nights down in their warm burrows.
If the rabbit gets too cold, it is more susceptible to chest infections, so don’t put them out for their outdoor exercise in wet, cold, and windy whether.
Rabbits quite enjoy a little light rain, so you could put them out for their exercise with a tarp for shelter
If possible give them their exercise indoors.
This is where my rabbits have their exercise on rainy days