The UNI 10349-3 provides, methods and summary tables relating to indices to be used for the description of the climate of the territory. The UNI 10349-3 completes the UNI EN ISO 15927-6 providing the calculation for determining, both in the cooling season and in the heating season of buildings, degree days, the cumulative differences of mixing ratio, global solar radiation accumulated on the horizontal plane and the Index of climatic severity "all weather".Theindices can be used for the the preliminary verification of technical systems.