The temperatures in Tromsø can vary throughout the Northern Lights season. In September, the average daily temperature is around 6.9°C, while in October it drops to 2.7°C. By November and December, temperatures reach -1.2°C and -3.4°C respectively. In January and February, expect temperatures around -4.4°C and -4.3°C, with a slight increase to -2.8°C in March. It's important to note that wind-chill factor can make it feel colder. To prevent frostbite, ensure you dress appropriately and take necessary precautions.