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Weather extremes

How extreme does Isahaya's weather get?

The hottest, coldest, wettest and snowiest days Isahaya 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 Nagasaki station 15 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 Isahaya has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day
102°F Aug 20, 2013

That is about 13°F hotter than a normal August afternoon in Isahaya (typical high near 89°F).

The three most extreme on record

1 102°F Aug 20, 2013
2 100°F Aug 19, 2013
3 100°F Aug 21, 2013
❄️ Coldest night
25°F Jan 24, 2016

About 15°F colder than a normal January night in Isahaya (typical low near 39°F).

The three most extreme on record

1 25°F Jan 24, 2016
2 27°F Jan 21, 2004
3 27°F Feb 2, 2012
🌧️ Most rain in one day
10.12 in Jul 11, 1993

The three most extreme on record

1 10.12 in Jul 11, 1993
2 10.12 in Aug 13, 1993
3 10.12 in Apr 4, 1994

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°30°50°70°90°110°130° all-time high 102°F JanFebMarAprMayJunJulAugSepOctNovDec
normal range of daily temperatureshottest ever recordedcoldest ever recorded

Isahaya's record heat sits well above even a hot day for the season — August's 102°F is about 13°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, Isahaya's warmest days reach the high 80s°F and its coldest nights drop to the high 30s°F. But across the record it has gone as high as 102°F and as low as 25°F. A single day has delivered over 10 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 Omura, about 15 km from the city centre.

How we build these numbers →