Guide 11 · Derived comparison
Which month has the highest precipitation normal in each city?
This page applies one transparent calculation to the 12 monthly precipitation normals for each selected observatory: identify the highest published total and keep the source value visible.
Calculation results
| Observatory | Month with highest listed normal | Precipitation normal (mm) |
|---|---|---|
| Sapporo | September | 142.2 |
| Tokyo | October | 234.8 |
| Osaka | June | 185.1 |
| Fukuoka | July | 299.1 |
| Naha | June | 284.4 |
What the calculation can support
The result identifies the maximum monthly total in each station’s 1991–2020 row. It is a compact way to compare seasonal patterns: the highest listed month is not the same across all five observatories. It does not show how rainfall is distributed within that month, how many days are wet, or whether a future month will match the historical total.
That limitation matters. A large monthly total can be concentrated in a short period or spread over many days. This page therefore labels the calculation rather than converting it into a daily-probability or itinerary claim.
Method and source. Highest value selected from each displayed station’s monthly precipitation row in JMA’s 1991–2020 Tables of Climatological Normals. This derived table is not a forecast.