You can use it in any weather. It is rated at IP67, which means it is: 6 - "Protected from total dust ingress" and 7 - "Protected from immersion between 15 centimetres and 1 metre in depth ".
I have to charge outside using an extension cord. I did cut off the ends of the extension cord and the charger cord and installed waterproof plugs. I freaked when I saw 4 conductors in the charger cord, but so far research and experience have shown that the 4th conductor doesn't do anything. I also wrapped the ends of the charger in 1-inch strips of neoprene, held in place with self-amalgamating tape, to protect the case better against scuffing on the ground than the little nubs molded into the case.
You should have at least a GFCI outlet. I installed a combo GFCI/AFCI breaker in the panel.
If your circuit will support it, be sure to crank the charger up to 12 amps.