The effect of constant and fluctuating temperatures on germination of Norway spruce (Picea abies(L.) Karst.) seeds collected from three individual trees was tested in darkness using a temperature‐gradient incubator. The germination probability of seeds was modeled between + 6.3 and + 29.1°C. Between minimum (+10°C) and optimum (+21°C) temperatures the probability fit well with a logistic curve reaching 50% germination at + 14.3°C. At temperatures above + 21°C the probability decreased, and the differences between trees were significant. At temperatures between + 10 and + 23°C the day degrees [Snk(T‐ 6°C)] with threshold temperature +6°C predicted germination rate reasonably well. At temperatures above +23°C germination rate was delayed significantly. The temperature fluctuation around mean temperature + 11.6°C did not effect the degree days required for germination. The increasing temperature fluctuation around mean temperature +24.3°C delayed germination. The seeds remaining dormant below and above optimum temperatures germinated after transfer to constant temperature (+ 22°C).