Guide 12 · Derived comparison
Sunshine hours in Japan: what a monthly total can and cannot show
Sunshine duration belongs beside temperature and precipitation in a climate comparison, but it should not be treated as a promise of clear skies or daylight on a chosen day.
Highest monthly sunshine-duration normal in each city
| Observatory | Month with highest listed normal | Sunshine duration (h) |
|---|---|---|
| Sapporo | May | 200.4 |
| Tokyo | January | 192.6 |
| Osaka | August | 222.4 |
| Fukuoka | May | 204.1 |
| Naha | July | 227.0 |
How to use the measure responsibly
These results use the same transparent method as the precipitation guide: choose the highest monthly value from each station’s displayed 12-month row. The months differ across the five selected locations, which makes a city-level comparison more informative than a nationwide assertion.
Sunshine duration is a recorded monthly total in the normal table. It is not identical to the length of the day, cloud cover at a particular hour, ultraviolet exposure, or an activity recommendation. Pair it with the temperature and precipitation figures, and use official forecasts when timing matters.
Method and source. Highest value selected from each station’s monthly sunshine-duration row in JMA’s 1991–2020 Tables of Climatological Normals. This is a historical comparison, not a forecast.