No. Do not expose power tools to rain or wet conditions. Water ingress increases the risk of electric shock, even with a battery-powered tool. It can also cause permanent damage to the tool and battery.
If you must work in a damp location, use a Ground Fault Circuit Interrupter (GFCI) protected supply for any battery charger. Keep the tool itself dry.
Heads up: After any use, keep handles and grasping surfaces dry, clean, and free from oil and grease. Store the tool and battery cartridge in a dry place.