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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 62°F (16°C). Winters average 39°F in January while summers reach 82°F in July. The area gets 294 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 51.7 inches (wetter than the 38-inch national average). The area receives 1.3 inches of snow annually. The city sits at an elevation of 16 feet.

Temperature

39°F Jan (4°C) 82°F Jul (28°C)
Annual Average61.5°F
14% above US avg
January Average39°F (4°C)
July Average82°F (28°C)
Sunny Days294 days/yr

Geography

Elevation16 ft (5 m)
Area64.6 sq mi (167.3 km²)
Population Density658/sq mi
Coordinates36.0500°N, 139.9000°W
TimezoneAsia/Tokyo

Precipitation & Snow

Annual Rainfall 51.7"
36% above US avg
Snowfall 1.3"
Wettest Month (Sep) 7.44"
Driest Month (Jan) 1.34"

Air Quality

Earthquake History

2,915 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M7.9.

Mar 11, 2011 47 km E of ?arai, Japan M7.9 112 km 43 km
May 7, 2008 78 km NE of Hasaki, Japan M6.9 147 km 27 km
Apr 11, 2011 17 km SSW of Ishikawa, Japan M6.6 115 km 11 km
Mar 11, 2011 81 km NE of Hasaki, Japan M6.5 150 km 7 km
Jun 1, 1990 near the east coast of Honshu, Japan M6.3 71 km 67 km
Jul 30, 2011 13 km SSE of Iwaki, Japan M6.3 137 km 38 km
Sep 11, 1996 23 km SSE of Hasaki, Japan M6.2 110 km 55 km
May 7, 2008 80 km NE of Hasaki, Japan M6.2 148 km 19 km
Apr 11, 2011 23 km SE of T?gane, Japan M6.2 93 km 15 km
Jun 3, 2000 6 km SE of Narut?, Japan M6.2 75 km 62 km
Apr 21, 2011 6 km WNW of T?gane, Japan M6.2 64 km 43 km
Sep 15, 2011 68 km E of ?arai, Japan M6.1 131 km 28 km
Aug 5, 1990 43 km E of ?arai, Japan M6.1 109 km 27 km
May 26, 2023 12 km SE of Narutō, Japan M6.1 81 km 42 km
Mar 11, 2011 4 km ESE of Hasaki, Japan M6.0 96 km 48 km
Mar 14, 2012 5 km SE of Asahi, Japan M6.0 82 km 10 km
Apr 3, 2004 37 km ESE of Hitachi, Japan M6.0 108 km 31 km
Aug 6, 1991 19 km E of Hasaki, Japan M6.0 109 km 29 km
Mar 15, 2011 6 km NNW of Fujinomiya, Japan M6.0 147 km 9 km
May 4, 2014 31 km ESE of It?, Japan M6.0 134 km 153 km
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.

Hurricane History

34 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 223 km
2024 Jebi Category 1 75 mph 244 km
2019 Faxai Category 3 98 mph 46 km
2019 Hagibis Category 2 92 mph 67 km
2018 Shanshan Category 1 75 mph 177 km
2018 Jongdari Category 1 81 mph 233 km
2016 Mindulle Category 1 75 mph 198 km
2016 Lionrock Category 1 81 mph 244 km
2014 Phanfone Category 1 81 mph 187 km
2011 Roke Category 2 92 mph 65 km
2009 Krovanh Category 1 69 mph 284 km
2007 Fitow Category 1 81 mph 81 km
2005 Saola Category 2 86 mph 286 km
2005 Mawar Category 2 81 mph 53 km
2004 Ma-on Category 3 92 mph 51 km
2002 Higos Category 2 86 mph 17 km
2001 Vipa Category 1 63 mph 281 km
2001 Danas Category 1 81 mph 28 km
2000 Sonamu Category 1 63 mph 288 km
2000 Kirogi Category 1 86 mph 110 km
Source: NOAA IBTrACS (Category 1+, 1980-2026).

Tsunami History

17 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 105,385 112 km
1495 KAMAKURA, SAGAMI BAY, TOKAIDO Earthquake 5.0 m 200 112 km
1732 KUJUKURI BEACH, JAPAN Earthquake 2.0 m - 125 km
1670 BOSO, JAPAN Earthquake 2.0 m - 117 km
1433 OFF IZU-OSHIMA Earthquake 2.0 m - 133 km
1978 TOKAIDO Earthquake 0.4 m 25 150 km
1923 RYUKYU ISLANDS Earthquake 0.3 m - 131 km
1896 KASHIMA, JAPAN Earthquake 0.3 m - 111 km
1935 JAPAN Earthquake 0.2 m - 148 km
1855 TOKAIDO Earthquake - 6,757 45 km
1782 ODAWARA, SAGAMI BAY Eruption + Earthquake - - 107 km
1642 BOSO, JAPAN Earthquake - - 114 km
1633 SAGAMI BAY Earthquake - 150 114 km
1602 BOSO, JAPAN Eruption + Earthquake - - 119 km
1257 SAGAMI BAY, JAPAN Earthquake - - 101 km
1241 KAMAKURA, SAGAMI BAY Earthquake - - 105 km
818 TOKAIDO Eruption + Earthquake - - 109 km
Source: NOAA/NCEI Historical Tsunami Database.

Nearby Volcanoes

15 volcanoes within 200 km. Closest: Akagisan (85 km).

Name Type Elevation Last Eruption Distance
Akagisan Stratovolcano 1,828 m (5,997 ft) Unknown 85 km
Nantaisan Stratovolcano 2,486 m (8,156 ft) -9540 88 km
Omanago Group Lava dome(s) 2,341 m (7,680 ft) -3050 90 km
Takaharayama Stratovolcano 1,795 m (5,889 ft) -4570 95 km
Nikko-Shiranesan Shield 2,578 m (8,458 ft) 1952 96 km
Harunasan Stratovolcano 1,449 m (4,754 ft) 550 105 km
Hiuchigatake Stratovolcano 2,356 m (7,730 ft) 1544 115 km
Nasudake Stratovolcano(es) 1,915 m (6,283 ft) 1963 120 km
Hakoneyama Complex 1,438 m (4,718 ft) 2015 121 km
Asamayama Complex 2,568 m (8,425 ft) 2019 130 km
Fujisan Stratovolcano 3,776 m (12,388 ft) 1708 131 km
Kusatsu-Shiranesan Stratovolcano(es) 2,165 m (7,103 ft) 2018 138 km
Yokodake Stratovolcano(es) 2,480 m (8,136 ft) 1200 142 km
Shiga Shield(s) 2,041 m (6,696 ft) Unknown 143 km
Izu-Tobu Pyroclastic cone(s) 1,406 m (4,613 ft) 1989 147 km
Source: Smithsonian Institution Global Volcanism Program (GVP).

Monthly Weather

Month Avg Temperature Precipitation Summary
January 39°F (4°C) 1.3 in Coldest, Driest
February 39°F (4°C) 2.1 in
March 45°F (7°C) 3.3 in
April 55°F (13°C) 4.3 in
May 63°F (17°C) 4.7 in
June 69°F (21°C) 6.3 in
July 82°F (28°C) 5.8 in Warmest
August 79°F (26°C) 5.7 in
September 72°F (22°C) 7.4 in Wettest
October 62°F (16°C) 6.4 in
November 52°F (11°C) 2.9 in
December 42°F (6°C) 1.5 in

Iwai has a seasonal temperature swing of 43°F / from 39°F in January to 82°F in July. Total annual precipitation is 51.6 inches, with September being the wettest month (7.4") and January the driest (1.3").

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