The climate of the reserve has important contrasts. The western part is strongly influenced by humid air from the nearby Atlantic ocean. It brings more mild temperatures in winter, while maintaining freshness in summer. The nearby Atlantic also provides a significant amount of rainfall. But the Norra Storfjället and mountains in its continuity to the north together with the Ammarfjället mountain range protect the eastern part of the reserve from the prevailing winds from west/southwest. This blocks the oceanic influence and creates a more continental climate. Thus, the Ammarnäs region, located in the rain shadow, receives less than 600 mm of precipitation per year, whereas Hemavan, not far away but located on the western side of Norra Storfjället, receives about 750 mm. In the mountains themselves, the amount of precipitation reaches 1200 mm in places. The growing season in Sweden, defined as the number of days when the average temperature exceed 5 °C, is about 120 days. Because of cooler temperatures, much of this precipitation is in the form of snow. The first snow fall, on average, is in early October in the middle of the valleys and snow cover usually persists