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Weather extremes

How extreme does Iwamizawa's weather get?

The hottest, coldest, wettest and snowiest days Iwamizawa 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 Iwamizawa station 3 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 Iwamizawa has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day
96°F Jul 31, 2021

That is about 19°F hotter than a normal July afternoon in Iwamizawa (typical high near 77°F).

The three most extreme on record

1 96°F Jul 31, 2021recent
2 95°F Aug 3, 2021
3 95°F Aug 6, 2021
❄️ Coldest night
-9°F Feb 7, 1998

About 24°F colder than a normal February night in Iwamizawa (typical low near 15°F).

The three most extreme on record

1 -9°F Feb 7, 1998
2 -7°F Feb 6, 1998
3 -6°F Jan 29, 1994
🌧️ Most rain in one day
4.88 in Aug 16, 2022

About 77% of a typical August's rain in a single day (Iwamizawa averages roughly 6.3 in across the month).

The three most extreme on record

1 4.88 in Aug 16, 2022recent
2 4.06 in Aug 31, 2019
3 4.02 in Aug 17, 2016

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.

-30°-10°10°30°50°70°90°110° all-time high 96°F JanFebMarAprMayJunJulAugSepOctNovDec
normal range of daily temperatureshottest ever recordedcoldest ever recorded

Iwamizawa's record heat sits well above even a hot day for the season — July's 96°F is about 19°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, Iwamizawa's warmest days reach the high 70s°F and its coldest nights drop to the mid-10s°F. But across the record it has gone as high as 96°F and as low as −9°F. A single day has delivered over 5 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 Iwamizawa, about 2 km from the city centre.

How we build these numbers →