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Weather extremes

How extreme does Unzen's weather get?

The hottest, coldest, wettest and snowiest days Unzen has recorded — the outer limits of what its weather can do, and how far they sit beyond a normal day.

Based on 34 years of daily weather observations (1991–present), from the Unzendake station 5 km away. Updated through August 2025 — an all-time extreme only changes when a more extreme day actually occurs, so some dates are old. That is normal, not stale data.

The four kinds of extreme

The hottest, coldest, wettest and snowiest single days Unzen has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day
92°F Jul 21, 1994

That is about 14°F hotter than a normal July afternoon in Unzen (typical high near 78°F).

The three most extreme on record

1 92°F Jul 21, 1994
2 92°F Aug 2, 2017
3 91°F Jul 16, 1994
❄️ Coldest night
14°F Jan 25, 2016

About 16°F colder than a normal January night in Unzen (typical low near 30°F).

The three most extreme on record

1 14°F Jan 25, 2016
2 15°F Jan 24, 2016
3 15°F Jan 25, 2023
🌧️ Most rain in one day
13.05 in Aug 10, 2025

More rain in a single day than Unzen usually gets in the whole month of August (typical August total about 11.2 in).

The three most extreme on record

1 13.05 in Aug 10, 2025recent
2 12.52 in Jun 24, 2012
3 12.48 in Jun 11, 2015

How hot and cold it gets, month by month

The shaded band is the normal range of daily temperatures for each month. The dots show the most extreme it has ever been — so you can see how far beyond a normal day the records really sit.

-10°10°30°50°70°90°110° all-time high 92°F JanFebMarAprMayJunJulAugSepOctNovDec
normal range of daily temperatureshottest ever recordedcoldest ever recorded

Unzen's record heat sits well above even a hot day for the season — July's 92°F is about 14°F beyond a normal hot afternoon. Its record cold is just as far below a normal winter night — the dots mark how rare each extreme really is.

In plain terms

In a normal year, Unzen's warmest days reach the low 80s°F and its coldest nights drop to the low 30s°F. But across the record it has gone as high as 92°F and as low as 14°F. A single day has delivered over 13 inches of rain. Those are the outer edges worth knowing if you are moving here, planning a trip, or thinking about a house.
Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from the Japan Meteorological Agency, measured at Unzendake, about 4 km from the city centre.

How we build these numbers →