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Weather & Climate in Iwanai, Japan
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Iwanai has a cool climate with an average annual temperature of 43°F (6°C). Winters average 20°F in January while summers reach 66°F in July. The area gets 235 sunny days per year, above the national average. Annual precipitation totals 55.6 inches (wetter than the 38-inch national average). The area receives 19.1 inches of snow annually, a moderate snowfall amount. The city sits at an elevation of 20 feet.
Temperature
20°F Jan (-7°C)
66°F Jul (19°C)
| Annual Average | 43.2°F |
| 20% below US avg | |
| January Average | 20°F (-7°C) |
| July Average | 66°F (19°C) |
| Sunny Days | 235 days/yr |
Geography
| Elevation | 20 ft (6 m) |
| Area | 126.6 sq mi (327.8 km²) |
| Population Density | 104/sq mi |
| Coordinates | 42.9744°N, 140.5089°W |
| Timezone | Asia/Tokyo |
Precipitation & Snow
Air Quality
Earthquake History
492 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M7.7.
| Jul 12, 1993 | 107 km W of Iwanai, Japan | M7.7 | 108 km | 17 km |
| Dec 22, 1996 | 131 km W of Iwanai, Japan | M6.5 | 132 km | 227 km |
| Aug 7, 1993 | 69 km WNW of Kamiiso, Japan | M6.5 | 123 km | 14 km |
| Jul 12, 1993 | 109 km W of Iwanai, Japan | M6.3 | 109 km | 33 km |
| Jun 11, 2023 | 20 km WSW of Biratori, Japan | M6.2 | 124 km | 121 km |
| Aug 24, 1992 | 9 km NNW of Honch?, Japan | M6.2 | 112 km | 121 km |
| Jul 12, 1993 | 101 km W of Iwanai, Japan | M6.0 | 101 km | 29 km |
| Jan 12, 2021 | 84 km NW of Yoichi, Japan | M5.9 | 91 km | 214 km |
| Jul 12, 1993 | 125 km WNW of Kamiiso, Japan | M5.6 | 148 km | 33 km |
| May 23, 1995 | Hokkaido, Japan region | M5.6 | 125 km | 17 km |
| Feb 28, 2009 | 37 km NW of Shizunai-furukawach?, Japan | M5.5 | 136 km | 105 km |
| Apr 18, 2007 | 21 km E of Tomakomai, Japan | M5.5 | 116 km | 120 km |
| Jul 8, 2014 | 13 km N of Shiraoi, Japan | M5.5 | 76 km | 10 km |
| Sep 19, 1993 | 111 km W of Iwanai, Japan | M5.5 | 111 km | 19 km |
| Feb 21, 2019 | 25 km ESE of Chitose, Japan | M5.4 | 120 km | 28 km |
| Jul 12, 1993 | 88 km W of Iwanai, Japan | M5.4 | 88 km | 33 km |
| Apr 12, 2018 | 110 km NW of Iwanai, Japan | M5.3 | 111 km | 217 km |
| Jul 1, 2017 | 22 km E of Chitose, Japan | M5.3 | 117 km | 37 km |
| Nov 3, 2001 | 115 km NW of Yoichi, Japan | M5.3 | 118 km | 221 km |
| Jul 16, 1993 | 94 km WNW of Iwanai, Japan | M5.3 | 95 km | 25 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Hurricane History
1 hurricane (Category 1+) recorded within 500 km since 1980. Strongest on record: Category 1.
| Year | Name | Category | Max Wind | Closest |
| 2002 | Higos | Category 1 | 69 mph | 285 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tsunami History
6 tsunamis recorded within 500 km. Highest wave on record: 32.0 m (105 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1993 | SEA OF JAPAN | Earthquake | 32.0 m | 231 | 108 km |
| 1640 | SE. HOKKAIDO ISLAND | Explosion | 8.0 m | 700 | 102 km |
| 1947 | W. HOKKAIDO ISLAND | Earthquake | 2.0 m | — | 100 km |
| 1993 | JAPAN | Earthquake | 0.2 m | — | 123 km |
| 1834 | W. HOKKAIDO ISLAND | Earthquake | — | — | 81 km |
| 1792 | W. HOKKAIDO ISLAND | Earthquake | — | — | 59 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
10 volcanoes within 200 km. Closest: Niseko (17 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Niseko | Stratovolcano(es) | 1,308 m (4,291 ft) | -4900 | 17 km |
| Yoteizan | Stratovolcano | 1,888 m (6,194 ft) | -1050 | 30 km |
| Toya | Stratovolcano | 733 m (2,405 ft) | 2001 | 55 km |
| Kuttara | Stratovolcano(es) | 549 m (1,801 ft) | 1820 | 76 km |
| Shikotsu | Caldera | 1,320 m (4,331 ft) | 1979 | 78 km |
| Hokkaido-Komagatake | Stratovolcano | 1,131 m (3,711 ft) | 2000 | 102 km |
| Esan | Lava dome(s) | 618 m (2,028 ft) | 1874 | 141 km |
| Tokachidake | Stratovolcano(es) | 2,077 m (6,814 ft) | 2004 | 183 km |
| Oshima-Oshima | Stratovolcano | 732 m (2,402 ft) | 1790 | 188 km |
| Osorezan | Stratovolcano | 878 m (2,881 ft) | 1787 | 195 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 20°F (-7°C) | 5.8 in | Coldest |
| February | 21°F (-6°C) | 4.3 in | |
| March | 28°F (-2°C) | 3.3 in | |
| April | 39°F (4°C) | 3.0 in | Driest |
| May | 49°F (10°C) | 3.0 in | |
| June | 57°F (14°C) | 3.2 in | |
| July | 66°F (19°C) | 4.5 in | |
| August | 68°F (20°C) | 6.0 in | Warmest, Wettest |
| September | 60°F (15°C) | 6.0 in | |
| October | 48°F (9°C) | 5.1 in | |
| November | 37°F (3°C) | 5.8 in | |
| December | 26°F (-3°C) | 5.8 in |
Iwanai has a seasonal temperature swing of 47°F / from 20°F in January to 68°F in August. Total annual precipitation is 55.6 inches, with August being the wettest month (6.0") and April the driest (3.0").