Iwaki climate
Iwaki (Japan) has a humid subtropical climate (Köppen Cfa). The average temperature over the year is 14 °C57 °F, and about 1,397 mm55 in of precipitation falls in an average year.
Temperature by month
Precipitation by month
Iwaki climate table
| Month | High °C°F | Low °C°F | Mean °C°F | Precip. mmin |
|---|---|---|---|---|
| Jan | 642 | −229 | 236 | 622.4 |
| Feb | 744 | −229 | 337 | 481.9 |
| Mar | 1152 | 134 | 643 | 883.5 |
| Apr | 1763 | 642 | 1153 | 1114.4 |
| May | 2272 | 1253 | 1762 | 1204.7 |
| Jun | 2678 | 1661 | 2170 | 1395.5 |
| Jul | 2985 | 2169 | 2577 | 1927.6 |
| Aug | 3087 | 2271 | 2679 | 1435.6 |
| Sep | 2679 | 1864 | 2272 | 1696.7 |
| Oct | 2069 | 1253 | 1661 | 1807.1 |
| Nov | 1559 | 642 | 1050 | 783.1 |
| Dec | 948 | 133 | 540 | 662.6 |
| Year | 3087 | −229 | 1457 | 1,39755 |
“Year” row: highest monthly high, lowest monthly low, annual mean and annual total.
| Month | Humid. | Cloud | Solar | Daylight |
|---|---|---|---|---|
| Jan | 85% | 66% | 2.2 | 9:53 |
| Feb | 83% | 67% | 2.9 | 10:47 |
| Mar | 80% | 66% | 3.8 | 11:51 |
| Apr | 80% | 67% | 4.7 | 13:06 |
| May | 80% | 70% | 5.2 | 14:08 |
| Jun | 84% | 78% | 4.9 | 14:41 |
| Jul | 85% | 80% | 4.4 | 14:28 |
| Aug | 84% | 72% | 4.5 | 13:34 |
| Sep | 86% | 74% | 3.7 | 12:22 |
| Oct | 86% | 70% | 3.0 | 11:10 |
| Nov | 86% | 64% | 2.3 | 10:08 |
| Dec | 86% | 65% | 1.9 | 9:38 |
Humid. = average relative humidity at 2 m; cloud = average cloud amount; solar = average daily solar energy reaching the ground in kWh/m² (all-sky); daylight in hours:minutes, calculated for the 15th of each month.
What the climate of Iwaki is like
The warmest month is August, with an average high of 30 °C87 °F and a low of 22 °C71 °F. The coldest is January, when highs average 6 °C42 °F and lows −2 °C29 °F. Seasons are strongly marked: the warmest month is on average 24.1 °C43.4 °F warmer than the coldest.
It is wet, with about 1,397 mm55 in of precipitation per year. The wettest three-month stretch is July–September, which brings 36% of the annual total. The wettest month is July (192 mm7.6 in), the driest is February (48 mm1.9 in).
Relative humidity ranges from 80% in April to 86% in November. The clearest skies (lowest average cloud amount, 64%) are typical of November. Average wind speed near the ground ranges from 1 km/h (1 mph) in July to 4 km/h (2 mph) in February. Daylight lasts from about 9.6 hours in December to 14.7 hours in June.
Best time to visit Iwaki
Based on these averages, the most comfortable months for sightseeing and outdoor activities are May: average highs of 22 °C72 °F to 22 °C72 °F with 120 mm4.7 in to 120 mm4.7 in of precipitation per month.
The most challenging month is January, which is cold, with average highs of 6 °C42 °F.
Comfort score: months are ranked by how close they come to an average high of 21–28 °C (70–82 °F), lows above 5 °C (41 °F), little precipitation and moderate humidity. The best-ranked months of each place are recommended, even where none meets all of these. These are general rules of thumb applied to long-term averages.
What to pack for Iwaki
- Winter (December–February) — highs 642 to 9 °C48 °F, lows −229 to 1 °C33 °F, about 59 mm2.3 in of precipitation a month. Pack a warm coat, layers and closed shoes and shoes with good grip, as frost is common.
- Spring (March–May) — highs 1152 to 22 °C72 °F, lows 134 to 12 °C53 °F, about 106 mm4.2 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket, an extra layer for the cooler mornings and evenings and an umbrella or light rain jacket.
- Summer (June–August) — highs 2678 to 30 °C87 °F, lows 1661 to 22 °C71 °F, about 158 mm6.2 in of precipitation a month. Pack light summer clothes such as T-shirts, shorts or light dresses and an umbrella or light rain jacket.
- Autumn (September–November) — highs 1559 to 26 °C79 °F, lows 642 to 18 °C64 °F, about 143 mm5.6 in of precipitation a month. Pack light layers — T-shirts plus a light sweater or jacket and an umbrella or light rain jacket.
How Iwaki compares
Compared with Utsunomiya, about 104 km to the southwest, Iwaki is on average 0.4 °C0.8 °F warmer and receives 5% less precipitation (1,397 mm55 in vs 1,474 mm58 in). The difference is largest in December (0.9 °C1.6 °F warmer).
Of the 111 places in Japan covered by World Climates, Iwaki is the 83rd warmest by annual mean temperature and the 95th wettest by annual precipitation. See all of them on the Japan climate page.
Places in other countries with the most similar temperature and rainfall pattern: Gyeongju (South Korea, Cfa), Atlantic City (United States, Cfa) and Pohang (South Korea, Cfa).
Nearby places
- Kōriyama 59 km · 12 °C53 °F · 1,302 mm51 in
- Nasushiobara 73 km · 12 °C54 °F · 1,405 mm55 in
- Fukushima 86 km · 12 °C54 °F · 1,363 mm54 in
- Mito 87 km · 15 °C58 °F · 1,479 mm58 in
- Aizu-Wakamatsu 96 km · 12 °C54 °F · 1,349 mm53 in
- Utsunomiya 104 km · 13 °C56 °F · 1,474 mm58 in
- Tsukuba 127 km · 15 °C59 °F · 1,519 mm60 in
- Sendai 135 km · 12 °C53 °F · 1,547 mm61 in
Frequently asked questions
What is the warmest month in Iwaki?
August is the warmest month in Iwaki, with an average high of 30 °C (87 °F) and an average low of 22 °C (71 °F).
What is the coldest month in Iwaki?
January is the coldest month, with an average high of 6 °C (42 °F) and an average low of -2 °C (29 °F).
When does it rain the most in Iwaki?
July is the wettest month with about 192 mm (7.6 in) of precipitation; February is the driest with about 48 mm (1.9 in).
What is the best time to visit Iwaki?
Judging by long-term averages, the most comfortable months are May.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 349 m, while Iwaki lies at about 9 m. Temperatures on this page were therefore adjusted by +2.2 °C4 °F using the standard lapse rate of 6.5 °C per 1,000 m.