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Weather & Climate in Iwai, Japan
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Iwai enjoys a temperate climate with an average annual temperature of 56°F (13°C). Winters average 37°F in January while summers reach 74°F in July. The area gets 234 sunny days per year, above the national average. Annual precipitation totals 56.3 inches (wetter than the 38-inch national average). The city sits at an elevation of 1,053 feet.
Temperature
37°F Jan (3°C)
74°F Jul (24°C)
| Annual Average | 56.0°F |
| 4% above US avg | |
| January Average | 37°F (3°C) |
| July Average | 74°F (24°C) |
| Sunny Days | 234 days/yr |
Geography
| Elevation | 1,053 ft (321 m) |
| Area | 17.7 sq mi (45.9 km²) |
| Population Density | 957/sq mi |
| Coordinates | 35.7500°N, 139.2333°W |
| Timezone | Asia/Tokyo |
Precipitation & Snow
Air Quality
Earthquake History
1,677 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M6.4.
| Feb 20, 1990 | 28 km E of Shimoda, Japan | M6.4 | 116 km | 14 km |
| Jun 1, 1990 | near the east coast of Honshu, Japan | M6.3 | 103 km | 67 km |
| Jun 3, 2000 | 6 km SE of Narut?, Japan | M6.2 | 113 km | 62 km |
| Apr 11, 2011 | 23 km SE of T?gane, Japan | M6.2 | 127 km | 15 km |
| Aug 10, 2009 | 8 km NE of Sagara, Japan | M6.2 | 142 km | 40 km |
| Apr 21, 2011 | 6 km WNW of T?gane, Japan | M6.2 | 99 km | 43 km |
| May 26, 2023 | 12 km SE of Narutō, Japan | M6.1 | 120 km | 42 km |
| Mar 11, 2011 | 4 km ESE of Hasaki, Japan | M6.0 | 148 km | 48 km |
| Mar 15, 2011 | 6 km NNW of Fujinomiya, Japan | M6.0 | 79 km | 9 km |
| Mar 14, 2012 | 5 km SE of Asahi, Japan | M6.0 | 132 km | 10 km |
| May 4, 2014 | 31 km ESE of It?, Japan | M6.0 | 95 km | 153 km |
| Apr 10, 2005 | near the east coast of Honshu, Japan | M5.9 | 107 km | 43 km |
| Jul 23, 2005 | 9 km WSW of Ichihara, Japan | M5.9 | 73 km | 61 km |
| Aug 1, 2011 | 20 km E of ?yama, Japan | M5.9 | 144 km | 13 km |
| Jan 15, 2007 | 15 km WSW of Heda, Japan | M5.9 | 110 km | 170 km |
| May 20, 2011 | 3 km NNE of Hasaki, Japan | M5.8 | 145 km | 29 km |
| Apr 29, 2012 | 5 km NNW of T?gane, Japan | M5.8 | 102 km | 44 km |
| Apr 16, 2011 | 6 km ENE of Tanuma, Japan | M5.8 | 79 km | 77 km |
| Feb 1, 1992 | 4 km SSE of Miura, Japan | M5.8 | 81 km | 100 km |
| Feb 25, 2013 | 29 km NE of Numata, Japan | M5.8 | 122 km | 10 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Hurricane History
36 hurricanes (Category 1+) recorded within 500 km since 1980. Strongest on record: Category 3.
| Year | Name | Category | Max Wind | Closest |
| 2024 | Ampil | Category 3 | 98 mph | 249 km |
| 2024 | Jebi | Category 1 | 75 mph | 289 km |
| 2019 | Faxai | Category 3 | 98 mph | 66 km |
| 2019 | Hagibis | Category 2 | 92 mph | 23 km |
| 2018 | Jongdari | Category 2 | 86 mph | 192 km |
| 2018 | Jebi | Category 1 | 81 mph | 292 km |
| 2018 | Shanshan | Category 1 | 81 mph | 200 km |
| 2016 | Mindulle | Category 1 | 75 mph | 163 km |
| 2014 | Phanfone | Category 1 | 81 mph | 121 km |
| 2011 | Roke | Category 2 | 92 mph | 17 km |
| 2009 | Krovanh | Category 1 | 69 mph | 258 km |
| 2007 | Fitow | Category 1 | 81 mph | 17 km |
| 2005 | Mawar | Category 2 | 81 mph | 72 km |
| 2004 | Ma-on | Category 3 | 92 mph | 54 km |
| 2003 | Etau | Category 1 | 52 mph | 275 km |
| 2002 | Higos | Category 2 | 86 mph | 62 km |
| 2001 | Danas | Category 1 | 81 mph | 60 km |
| 2001 | Vipa | Category 1 | 63 mph | 288 km |
| 2000 | Kirogi | Category 1 | 86 mph | 142 km |
| 1998 | Vicki | Category 2 | 69 mph | 188 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tsunami History
20 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 | 76 km |
| 1703 | OFF SW BOSO PENINSULA | Earthquake | 11.7 m | 5,233 | 128 km |
| 1495 | KAMAKURA, SAGAMI BAY, TOKAIDO | Earthquake | 5.0 m | 200 | 76 km |
| 1433 | OFF IZU-OSHIMA | Earthquake | 2.0 m | — | 98 km |
| 2009 | HONSHU: S COAST | Earthquake | 0.6 m | 1 | 142 km |
| 1980 | HONSHU ISLAND | Earthquake | 0.6 m | — | 105 km |
| 1978 | TOKAIDO | Earthquake | 0.4 m | 25 | 105 km |
| 1923 | RYUKYU ISLANDS | Earthquake | 0.3 m | — | 129 km |
| 1974 | TOKAIDO | Earthquake | 0.2 m | 30 | 137 km |
| 1990 | JAPAN | Earthquake | 0.2 m | — | 116 km |
| 1857 | TOKAIDO | Earthquake | — | — | 135 km |
| 1855 | TOKAIDO | Earthquake | — | 6,757 | 52 km |
| 1782 | ODAWARA, SAGAMI BAY | Eruption + Earthquake | — | — | 84 km |
| 1642 | BOSO, JAPAN | Earthquake | — | — | 138 km |
| 1633 | SAGAMI BAY | Earthquake | — | 150 | 61 km |
| 1602 | BOSO, JAPAN | Eruption + Earthquake | — | — | 136 km |
| 1589 | SURUGA, JAPAN | Earthquake | — | — | 141 km |
| 1257 | SAGAMI BAY, JAPAN | Earthquake | — | — | 66 km |
| 1241 | KAMAKURA, SAGAMI BAY | Earthquake | — | — | 63 km |
| 818 | TOKAIDO | Eruption + Earthquake | — | — | 62 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
15 volcanoes within 200 km. Closest: Hakoneyama (61 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Hakoneyama | Complex | 1,438 m (4,718 ft) | 2015 | 61 km |
| Fujisan | Stratovolcano | 3,776 m (12,388 ft) | 1708 | 63 km |
| Harunasan | Stratovolcano | 1,449 m (4,754 ft) | 550 | 88 km |
| Akagisan | Stratovolcano | 1,828 m (5,997 ft) | Unknown | 90 km |
| Yokodake | Stratovolcano(es) | 2,480 m (8,136 ft) | 1200 | 90 km |
| Izu-Tobu | Pyroclastic cone(s) | 1,406 m (4,613 ft) | 1989 | 95 km |
| Asamayama | Complex | 2,568 m (8,425 ft) | 2019 | 97 km |
| Izu-Oshima | Stratovolcano | 758 m (2,487 ft) | 1990 | 115 km |
| Nantaisan | Stratovolcano | 2,486 m (8,156 ft) | -9540 | 115 km |
| Kusatsu-Shiranesan | Stratovolcano(es) | 2,165 m (7,103 ft) | 2018 | 115 km |
| Nikko-Shiranesan | Shield | 2,578 m (8,458 ft) | 1952 | 117 km |
| Omanago Group | Lava dome(s) | 2,341 m (7,680 ft) | -3050 | 119 km |
| Shiga | Shield(s) | 2,041 m (6,696 ft) | Unknown | 122 km |
| Hiuchigatake | Stratovolcano | 2,356 m (7,730 ft) | 1544 | 134 km |
| Takaharayama | Stratovolcano | 1,795 m (5,889 ft) | -4570 | 137 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 37°F (3°C) | 1.5 in | Coldest, Driest |
| February | 38°F (3°C) | 2.0 in | |
| March | 43°F (6°C) | 3.2 in | |
| April | 54°F (12°C) | 4.0 in | |
| May | 62°F (17°C) | 5.1 in | |
| June | 68°F (20°C) | 7.4 in | |
| July | 74°F (24°C) | 6.1 in | |
| August | 77°F (25°C) | 8.0 in | Warmest |
| September | 70°F (21°C) | 8.2 in | Wettest |
| October | 60°F (15°C) | 6.4 in | |
| November | 50°F (10°C) | 2.8 in | |
| December | 41°F (5°C) | 1.5 in |
Iwai has a seasonal temperature swing of 40°F / from 37°F in January to 77°F in August. Total annual precipitation is 56.3 inches, with September being the wettest month (8.2") and January the driest (1.5").