The derailleur can shift a little during the winter. It is best to try out the individual gears one after the other. If there are problems, you can make fine adjustments using the tension screw (at the point where the cables enter the gears).
Even if you think you will only ride your bike during the day, you need a functioning light. For bicycles with a dynamo, simply switch it on for a short ride. If no light comes on, check the cables and plug connections. If you have battery-operated lights, switch them on briefly for a check and, to be on the safe side, recharge them before your first ride.