Mo i Rana's climate is usually classified as subarctic (K�ppen Dfc), with long, cold winters, and short, warm summers. The Norwegian Current (extension of Gulf Stream), follows the coastline of Norway all the way north. The stream has a heavy influence on the climate, helping to keep the temperatures from getting too low in the winter, despite the city being located about 70 kilometres (43 mi) from the coast line. The distance from the coast, however, does give it slightly lower temperatures in the winter than towns nearer the coast. The weather can be very unpredictable, and change quickly. Blizzards can go on for hours, potentially creating traffic difficulties and cancelling flights. Because of Mo i Rana's latitude, summer days are very long and winter days are very short on daylight. In the winter season, the Northern Lights can be seen on the night sky. It varies in intensity, coloured from white green to deep red, and comes in different shapes, such as beams, arches and draperies.
The summer is short; July and August are the warmest months. The 24-hr average temperature in July is 13.2 �C (55.8 �F). This is based on the 1961-1990 base period; recent years have tended to be warmer in this area. There are usually two to three warm periods during the summer, when the average temperature is between 20 and 26 �C (68 and 79 �F) at daytime. The warm days may last for 2�14 days, with the temperature peaking at 31 �C (88 �F). Occasionally, the temperatures stay over 20 �C (68 �F) even at night time, a phenomenon called tropenatt in Norwegian.
Autumn begins in September. The trees lose their leaves in October, and the flowers disappear. During November, fresh water and rivers start to freeze, and the landscape is covered with snow. Only the spruce forest stays green throughout the winter. In the winter, the sun is low on the horizon, and is only visible for a few hours. Heating through sunlight is limited because of Mo i Rana's high-latitude location
