Some of the spectacular roads leading to Geiranger are passing over rough mountain terrain which has to be closed during the winter due to high risk for snow avalanches. This is true for part of the Trollstigen road (road 63), between Åndalsnes and Valldal.
The same is valid for the stretch over the Geiranger mountain between Geiranger and Langvatn to the crossroad at road no 15. Normally both mountain passes are closed in the period mid November to mid May, but it may varied in harmony with the snow conditions.
To be sure these roads are open you can check the Norwegian Public Roads Administration's map for traffic information. If the road is marked with a cross and the word VINTER it means the road is still closed due to snow condition:
Even if these roads are closed, you can get to Geiranger all year round. More information about how to get here.