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Weather & Climate in Iwamotochō, Japan
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Iwamotochō enjoys a temperate climate with an average annual temperature of 63°F (17°C). Winters average 42°F in January while summers reach 82°F in July. The area gets 283 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 50.3 inches (wetter than the 38-inch national average). The city sits at an elevation of 62 feet.
Temperature
42°F Jan (6°C)
82°F Jul (28°C)
| Annual Average | 63.1°F |
| 17% above US avg | |
| January Average | 42°F (6°C) |
| July Average | 82°F (28°C) |
| Sunny Days | 283 days/yr |
Geography
| Elevation | 62 ft (19 m) |
| Area | 4.9 sq mi (12.6 km²) |
| Population Density | 677/sq mi |
| Coordinates | 35.6941°N, 139.7770°W |
| Timezone | Asia/Tokyo |
Precipitation & Snow
Air Quality
Earthquake History
2,534 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M7.9.
| Mar 11, 2011 | 47 km E of ?arai, Japan | M7.9 | 137 km | 43 km |
| Feb 20, 1990 | 28 km E of Shimoda, Japan | M6.4 | 120 km | 14 km |
| Jun 1, 1990 | near the east coast of Honshu, Japan | M6.3 | 54 km | 67 km |
| Apr 11, 2011 | 23 km SE of T?gane, Japan | M6.2 | 79 km | 15 km |
| Sep 11, 1996 | 23 km SSE of Hasaki, Japan | M6.2 | 107 km | 55 km |
| Jun 3, 2000 | 6 km SE of Narut?, Japan | M6.2 | 64 km | 62 km |
| Apr 21, 2011 | 6 km WNW of T?gane, Japan | M6.2 | 49 km | 43 km |
| Jun 5, 2012 | 75 km ESE of ?hara, Japan | M6.1 | 149 km | 15 km |
| Aug 5, 1990 | 43 km E of ?arai, Japan | M6.1 | 135 km | 27 km |
| May 26, 2023 | 12 km SE of Narutō, Japan | M6.1 | 70 km | 42 km |
| Apr 3, 2004 | 37 km ESE of Hitachi, Japan | M6.0 | 138 km | 31 km |
| Mar 14, 2012 | 5 km SE of Asahi, Japan | M6.0 | 83 km | 10 km |
| Mar 15, 2011 | 6 km NNW of Fujinomiya, Japan | M6.0 | 118 km | 9 km |
| Jan 9, 1995 | 48 km ENE of Hasaki, Japan | M6.0 | 143 km | 33 km |
| Jul 20, 2000 | 31 km ESE of Hitachi, Japan | M6.0 | 141 km | 47 km |
| Aug 6, 1991 | 19 km E of Hasaki, Japan | M6.0 | 114 km | 29 km |
| Mar 11, 2011 | 4 km ESE of Hasaki, Japan | M6.0 | 99 km | 48 km |
| May 4, 2014 | 31 km ESE of It?, Japan | M6.0 | 93 km | 153 km |
| Jun 24, 2020 | 36 km SE of Hasaki, Japan | M5.9 | 120 km | 29 km |
| Jul 23, 2005 | 9 km WSW of Ichihara, Japan | M5.9 | 29 km | 61 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Hurricane History
38 hurricanes (Category 1+) recorded within 500 km since 1980. Strongest on record: Category 4.
| Year | Name | Category | Max Wind | Closest |
| 2025 | Nakri | Category 1 | — | 291 km |
| 2024 | Ampil | Category 3 | 98 mph | 205 km |
| 2024 | Jebi | Category 1 | 75 mph | 241 km |
| 2019 | Faxai | Category 4 | 98 mph | 24 km |
| 2019 | Hagibis | Category 2 | 92 mph | 36 km |
| 2018 | Jongdari | Category 2 | 86 mph | 192 km |
| 2018 | Shanshan | Category 1 | 81 mph | 156 km |
| 2016 | Mindulle | Category 1 | 75 mph | 157 km |
| 2016 | Lionrock | Category 1 | 75 mph | 256 km |
| 2014 | Phanfone | Category 1 | 81 mph | 153 km |
| 2011 | Roke | Category 2 | 92 mph | 57 km |
| 2009 | Krovanh | Category 1 | 69 mph | 244 km |
| 2007 | Fitow | Category 1 | 81 mph | 53 km |
| 2005 | Saola | Category 2 | 86 mph | 264 km |
| 2005 | Mawar | Category 2 | 86 mph | 35 km |
| 2004 | Ma-on | Category 4 | 92 mph | 11 km |
| 2003 | Choi-wan | Category 3 | 81 mph | 280 km |
| 2002 | Higos | Category 2 | 86 mph | 25 km |
| 2002 | Phanfone | Category 1 | 75 mph | 289 km |
| 2001 | Vipa | Category 1 | 69 mph | 252 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tsunami History
19 tsunamis recorded within 500 km. Highest wave on record: 13.0 m (43 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1923 | SAGAMI BAY | Earthquake | 13.0 m | 105,385 | 71 km |
| 1703 | OFF SW BOSO PENINSULA | Earthquake | 11.7 m | 5,233 | 111 km |
| 1495 | KAMAKURA, SAGAMI BAY, TOKAIDO | Earthquake | 5.0 m | 200 | 71 km |
| 1732 | KUJUKURI BEACH, JAPAN | Earthquake | 2.0 m | — | 108 km |
| 1670 | BOSO, JAPAN | Earthquake | 2.0 m | — | 113 km |
| 1433 | OFF IZU-OSHIMA | Earthquake | 2.0 m | — | 92 km |
| 1980 | HONSHU ISLAND | Earthquake | 0.6 m | — | 112 km |
| 1978 | TOKAIDO | Earthquake | 0.4 m | 25 | 109 km |
| 1923 | RYUKYU ISLANDS | Earthquake | 0.3 m | — | 96 km |
| 1896 | KASHIMA, JAPAN | Earthquake | 0.3 m | — | 142 km |
| 1990 | JAPAN | Earthquake | 0.2 m | — | 120 km |
| 1855 | TOKAIDO | Earthquake | — | 6,757 | 5 km |
| 1782 | ODAWARA, SAGAMI BAY | Eruption + Earthquake | — | — | 66 km |
| 1642 | BOSO, JAPAN | Earthquake | — | — | 93 km |
| 1633 | SAGAMI BAY | Earthquake | — | 150 | 76 km |
| 1602 | BOSO, JAPAN | Eruption + Earthquake | — | — | 93 km |
| 1257 | SAGAMI BAY, JAPAN | Earthquake | — | — | 60 km |
| 1241 | KAMAKURA, SAGAMI BAY | Earthquake | — | — | 65 km |
| 818 | TOKAIDO | Eruption + Earthquake | — | — | 70 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
15 volcanoes within 200 km. Closest: Hakoneyama (86 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Hakoneyama | Complex | 1,438 m (4,718 ft) | 2015 | 86 km |
| Fujisan | Stratovolcano | 3,776 m (12,388 ft) | 1708 | 102 km |
| Izu-Tobu | Pyroclastic cone(s) | 1,406 m (4,613 ft) | 1989 | 108 km |
| Akagisan | Stratovolcano | 1,828 m (5,997 ft) | Unknown | 110 km |
| Izu-Oshima | Stratovolcano | 758 m (2,487 ft) | 1990 | 113 km |
| Harunasan | Stratovolcano | 1,449 m (4,754 ft) | 550 | 120 km |
| Nantaisan | Stratovolcano | 2,486 m (8,156 ft) | -9540 | 122 km |
| Omanago Group | Lava dome(s) | 2,341 m (7,680 ft) | -3050 | 125 km |
| Nikko-Shiranesan | Shield | 2,578 m (8,458 ft) | 1952 | 128 km |
| Takaharayama | Stratovolcano | 1,795 m (5,889 ft) | -4570 | 134 km |
| Asamayama | Complex | 2,568 m (8,425 ft) | 2019 | 138 km |
| Toshima | Stratovolcano | 508 m (1,667 ft) | -4550 | 138 km |
| Yokodake | Stratovolcano(es) | 2,480 m (8,136 ft) | 1200 | 138 km |
| Hiuchigatake | Stratovolcano | 2,356 m (7,730 ft) | 1544 | 147 km |
| Niijima | Lava dome(s) | 432 m (1,417 ft) | 886 | 151 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 42°F (6°C) | 1.7 in | |
| February | 42°F (6°C) | 2.3 in | Coldest |
| March | 47°F (9°C) | 4.0 in | |
| April | 58°F (14°C) | 4.7 in | |
| May | 66°F (19°C) | 5.1 in | |
| June | 71°F (22°C) | 6.9 in | |
| July | 82°F (28°C) | 6.2 in | Warmest |
| August | 81°F (27°C) | 6.2 in | |
| September | 74°F (23°C) | 8.0 in | Wettest |
| October | 64°F (18°C) | 6.6 in | |
| November | 54°F (12°C) | 3.4 in | |
| December | 45°F (7°C) | 1.6 in | Driest |
Iwamotochō has a seasonal temperature swing of 40°F / from 42°F in February to 82°F in July. Total annual precipitation is 56.4 inches, with September being the wettest month (8.0") and December the driest (1.6").