Climate averages 1991–2020
Isahaya weather
in December.
A cool, wet month: the 10th warmest and the 2nd driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
December is a cool month in Isahaya: daytime highs average 11.6°C and nights cool to about 7.7°C. By daytime temperature it is the 10th warmest of the 12 months.
Expect about 92 mm of rain on roughly 10 days, which makes December a wet month (the 2nd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 10 h 02 min on an average December day.
The nearest other city in this atlas is Ōmura (12 km away). In December its highs average 12.0°C, about as warm as Isahaya, with 75 mm of rain.
Among the 303 cities listed in Japan, Isahaya ranks joint 28th of 303 for the warmest December highs and joint 252nd of 303 for the driest December (rainfall, lowest first). The mean December high of those 303 cities is 9.5°C; Isahaya is 2.1°C warmer than that mean.
From December to January, average highs fall by 2.3°C to 9.3°C, and monthly rainfall falls from 92 mm to 79 mm.
The annual picture
December in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Isahaya climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 9.3°C5.5°C | 5.5°C | 79 | 10.9 | 10.210 h |
| February | 10.2°C5.6°C | 5.6°C | 100 | 10.2 | 11.011 h |
| March | 13.2°C7.9°C | 7.9°C | 149 | 12.0 | 12.012 h |
| April | 17.4°C11.6°C | 11.6°C | 167 | 11.4 | 13.013 h |
| May | 21.3°C15.8°C | 15.8°C | 197 | 10.8 | 13.814 h |
| June | 24.0°C19.6°C | 19.6°C | 444 | 16.5 | 14.314 h |
| July | 27.5°C23.6°C | 23.6°C | 346 | 16.6 | 14.114 h |
| August | 29.1°C24.8°C | 24.8°C | 185 | 13.7 | 13.413 h |
| September | 26.5°C21.9°C | 21.9°C | 202 | 11.9 | 12.412 h |
| October | 21.9°C17.3°C | 17.3°C | 112 | 7.5 | 11.411 h |
| November | 16.8°C12.4°C | 12.4°C | 106 | 9.1 | 10.511 h |
| December, selected | 11.6°C7.7°C | 7.7°C | 92 | 10.3 | 10.010 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
December in nearby cities
- Ōmura in DecemberJapan · 12 kmHigh 12.0°C · Low 8.0°C · 75 mm rain
- Nagasaki in DecemberJapan · 18 kmHigh 12.2°C · Low 8.6°C · 92 mm rain
- Ōmuta in DecemberJapan · 44 kmHigh 11.5°C · Low 5.6°C · 72 mm rain
- Amakusa in DecemberJapan · 45 kmHigh 12.5°C · Low 7.5°C · 81 mm rain
- Sasebo in DecemberJapan · 47 kmHigh 11.7°C · Low 7.3°C · 69 mm rain
- Saga in DecemberJapan · 50 kmHigh 11.3°C · Low 5.0°C · 71 mm rain
- Kumamoto in DecemberJapan · 61 kmHigh 11.2°C · Low 4.9°C · 84 mm rain
- Honmachi in DecemberJapan · 64 kmHigh 11.8°C · Low 5.1°C · 83 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Isahaya) is explained once on the Isahaya year overview and on the Sources, method and limits page.
Nagasaki lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.