Climate averages 1991–2020
Oyama weather
by month.
See how the year changes. August has the highest average daily maximum; December has the lowest average monthly rainfall.
Long-term climate patterns, not a forecast for a particular trip.
Across the year Oyama averages a daytime high of 18.4°C and a nighttime low of 9.6°C, with about 1,583 mm of rain on roughly 149 days. August is the warmest month (average high 29.5°C) and January the coolest (7.3°C). July is the wettest month with 209 mm; December is the driest with 54 mm.
The annual picture
A year in Oyama
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
Oyama climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 7.3°C-2.1°C | -2.1°C | 55 | 6.0 | 10.010 h |
| February | 8.4°C-1.5°C | -1.5°C | 55 | 6.9 | 10.811 h |
| March | 12.2°C1.6°C | 1.6°C | 106 | 11.6 | 11.912 h |
| April | 17.4°C6.8°C | 6.8°C | 120 | 12.6 | 13.113 h |
| May | 22.1°C12.4°C | 12.4°C | 153 | 13.7 | 14.114 h |
| June | 24.7°C16.9°C | 16.9°C | 177 | 16.5 | 14.615 h |
| July | 28.2°C21.0°C | 21.0°C | 209 | 18.7 | 14.414 h |
| August | 29.5°C22.3°C | 22.3°C | 161 | 16.3 | 13.514 h |
| September | 25.7°C18.9°C | 18.9°C | 206 | 16.2 | 12.412 h |
| October | 20.2°C12.7°C | 12.7°C | 200 | 13.9 | 11.311 h |
| November | 14.9°C5.9°C | 5.9°C | 88 | 9.4 | 10.310 h |
| December | 9.7°C0.4°C | 0.4°C | 54 | 6.8 | 9.710 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
Nearby cities
- TochigiJapan · 11 kmHigh 18.2°C · Low 9.5°C · 1,796 mm rain a year
- KogaJapan · 15 kmHigh 18.7°C · Low 9.9°C · 1,583 mm rain a year
- ChikuseiJapan · 16 kmHigh 18.7°C · Low 10.0°C · 1,358 mm rain a year
- SanoJapan · 20 kmHigh 18.4°C · Low 9.7°C · 1,626 mm rain a year
- MookaJapan · 24 kmHigh 18.4°C · Low 9.3°C · 1,344 mm rain a year
- TatebayashiJapan · 25 kmHigh 18.4°C · Low 9.7°C · 1,626 mm rain a year
- KazoJapan · 27 kmHigh 18.9°C · Low 10.1°C · 1,408 mm rain a year
- KukichūōJapan · 28 kmHigh 18.9°C · Low 10.1°C · 1,368 mm rain a year
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 limitsWhat do the high and low temperatures mean?
We average the daily maximum and daily minimum for each calendar month over 1991–2020. They are not record extremes, a forecast range or temperatures at a fixed time of day.
How is a rain day counted?
A local calendar day (standard time, UTC+9, no daylight saving) with at least 1 mm of total precipitation counts as one rain day. We count these for each year and month, then average across 30 years. The average does not predict which days will be wet.
Where do the numbers come from?
ERA5-Land (temperature) and ERA5 (precipitation) reanalysis from the Copernicus Climate Change Service, read from the Open-Meteo open-data archive. Temperature comes from the 0.1° model cell at 36.30°, 139.80° (0 km from the city centre), adjusted down by 0.2°C for the difference between the city's elevation (41 m) and the cell's (13 m). Rain comes from the 0.25° cell at 36.25°, 139.75°. Koga lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells. These are model estimates, not weather-station readings; coast, hills and city streets can differ.
Does this page show sunshine, humidity or sea temperature?
No. The data used here contain air temperature and precipitation only. Daylight hours are calculated from the city's latitude (sunrise to sunset), not measured sunshine.