No. Do not expose power tools to rain or wet conditions. Water entering the tool increases the risk of electric shock, even with a battery.
Stop work immediately. If operating in a damp location is unavoidable, you must use a Ground Fault Circuit Interrupter (GFCI) protected supply for the battery charger. This does not make the tool itself safe for use in rain.
HEADS UP: The charger is also not for outdoor use unless you provide a dry location and use an extension cord suitable for outdoor use. Using a cord suitable for outdoor use reduces the risk of electric shock.