jma_logo Welcome to TCC wmo_logo
World Climate
Climate System Monitoring
El Niño Monitoring
NWP Model Prediction
Global Warming
Climate in Japan
Training Module
Press release
HOME > World Climate > Explanation of Climatological Normals

Climatological Normals

Climatological normals of monthly temperature and precipitation are defined as 30-year averages, where the current base period is 1991 – 2020. The current normal data are based on GHCN (Global Historical Climatology Network) monthly data※1 provided by NCEI (the USA's National Centers for Environmental Information) and CLIMAT reports archived at TCC/JMA, but daily data were used for Japanese weather stations. CLIMAT reports contain monthly statistics relating to various meteorological elements from individual weather stations for a specific month, such as monthly mean temperature and monthly precipitation totals. Normals were calculated only where at least eight years for entire monthly data were available in the base period.

  ※1 GHCN ver. 4 [monthly mean temperature], Menne et al. (2017), NOAA NCEI, doi:10.7289/V5XW4GTH [accessed 31 March 2023].
    GHCN ver. 2 [monthly precipitation], Peterson and Vose (1997), NOAA NCEI, doi:10.7289/V5X34VDR [accessed 31 March 2023].


Normal & Historical Data

Tokyo Climate Center, Climate Prediction Division.
Copyright(C) 2002. Japan Meteorological Agency. All rights reserved. - Copyright & Disclaimer -