PURPOSE: To automate decision on the weather condition, fine or cloudy, by measuring the radiation of sunshine with a pyrheliometer and a radiation balance meter to compare the resulting value with the reference value at the measuring point.

CONSTITUTION: A weather meter is made up of a pyrheliometer 4, a radiation balance meter 5, a decision section 6, a timepiece section 7 and output section 8. The decision section 6 determines the sunrise time, sunset time and the meridian time by a signal of the timepiece section 7 to calculate the reference sunshine value from the results and the attained amount of sunshine. Then, section 6 compares the measured values of the pyrheliometer 4 and the radiation balance meter 5 with the reference sunshine value to decide on the weather condition, fine or cloudy by determining the amount of cloud. The results are outputted from the output section 8 thereby enabling the automation of the decision on the weather condition, fine or cloudy.