Isumi weather in August
In August, Isumi sees average daytime highs of 28°C and overnight lows near 25°C, with 100 mm of rain across 11 wet days and about 13.3 hours of daylight. It is the 1st-warmest and 12th-wettest month of the year here.
Day-to-day highs hold fairly steady near 28°C through the month. The sky is clear or mostly clear about 33% of the time in August, and the air most often feels miserable.
Daylight stretches from about 13 h 48 min at the start of August to 12 h 48 min by month's end. Set against the rest of the year, August is Isumi's 5th-clearest and 12th-windiest month. For the whole year in context, see Isumi's year-round climate.
- Daytime high
- 28°
- 1st warmest
- Overnight low
- 25°
- 12th coldest
- Rainfall
- 100 mm
- 11 wet days
- Daylight
- 13 h 18 min
- 5:02 AM – 6:23 PM
- Cloud cover
- 59%
- 5th clearest
- Wind
- 16 km/h
- 12th windiest
- Solar energy
- 5.53 kWh/m²
- Travel score
- 6.2
- out of 10
Isumi is city in Chiba Prefecture, Japan.
- Density
- 226/km²
- people per km²
- Founded
- 2005
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Temperature in August
Day-to-day highs hold fairly steady near 28°C through the month.
A typical August day in Isumi reaches about 28°C in the afternoon and slips back to 25°C overnight — a 3°C spread between the day's warmth and the night's chill. On most days the high lands between 25°C and 29°C. Set against its neighbours, August runs about 2°C warmer than July and about 2°C warmer than September.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 28 | 27 | 27 | 27 | 27 | 27 | 27 | 27 |
| Avg low (°C) | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 | 25 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| 1 | 28 | 25 |
| 2 | 28 | 25 |
| 3 | 28 | 25 |
| 4 | 28 | 25 |
| 5 | 28 | 25 |
| 6 | 28 | 25 |
| 7 | 28 | 25 |
| 8 | 28 | 25 |
| 9 | 28 | 25 |
| 10 | 28 | 25 |
| 11 | 28 | 25 |
| 12 | 28 | 25 |
| 13 | 28 | 25 |
| 14 | 28 | 25 |
| 15 | 28 | 25 |
| 16 | 28 | 25 |
| 17 | 28 | 25 |
| 18 | 28 | 25 |
| 19 | 28 | 25 |
| 20 | 28 | 25 |
| 21 | 28 | 25 |
| 22 | 28 | 25 |
| 23 | 28 | 25 |
| 24 | 28 | 25 |
| 25 | 27 | 25 |
| 26 | 27 | 25 |
| 27 | 27 | 25 |
| 28 | 27 | 25 |
| 29 | 27 | 25 |
| 30 | 27 | 25 |
| 31 | 27 | 25 |
Isumi weather by month
How August compares with the rest of the year at a glance. August is the 1st-warmest and 12th-wettest month here — the current month is highlighted below.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 10° / 7° | 108 | 10.7 | 9.9 | 2.5 |
| Feb | 11° / 6° | 101 | 10.6 | 10.7 | 2.4 |
| Mar | 13° / 9° | 159 | 14.6 | 11.7 | 3.2 |
| Apr | 16° / 13° | 126 | 12.6 | 12.9 | 4.8 |
| May | 20° / 17° | 138 | 11.8 | 13.8 | 5.9 |
| Jun | 23° / 20° | 190 | 13.5 | 14.3 | 5.8 |
| Jul | 26° / 24° | 133 | 11.8 | 14.1 | 6.2 |
| Aug | 28° / 25° | 100 | 11 | 13.3 | 6.2 |
| Sep | 25° / 23° | 188 | 14.7 | 12.2 | 5.9 |
| Oct | 21° / 19° | 239 | 14.9 | 11.1 | 5.8 |
| Nov | 17° / 14° | 147 | 13.4 | 10.1 | 5.2 |
| Dec | 13° / 9° | 106 | 11.7 | 9.7 | 3.6 |
Cloud cover in August
The sky is clear or mostly clear about 33% of the time in August.
Beyond those clear spells, partly cloudy skies cover about 15% of August, with mostly cloudy or overcast conditions the remaining 53%.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 43 | 43 | 43 | 44 | 45 | 45 | 45 | 46 | 46 | 47 | 47 | 47 | 48 | 48 | 49 | 49 | 49 | 49 | 49 | 49 | 49 | 49 | 48 | 49 | 48 | 48 | 48 | 49 | 49 | 48 | 48 |
| Cloudier (%) | 57 | 57 | 57 | 56 | 55 | 55 | 55 | 54 | 54 | 53 | 53 | 53 | 52 | 52 | 51 | 51 | 51 | 51 | 51 | 51 | 51 | 51 | 52 | 51 | 52 | 52 | 52 | 51 | 51 | 52 | 52 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| 1 | 43 | 57 |
| 2 | 43 | 57 |
| 3 | 43 | 57 |
| 4 | 44 | 56 |
| 5 | 45 | 55 |
| 6 | 45 | 55 |
| 7 | 45 | 55 |
| 8 | 46 | 54 |
| 9 | 46 | 54 |
| 10 | 47 | 53 |
| 11 | 47 | 53 |
| 12 | 47 | 53 |
| 13 | 48 | 52 |
| 14 | 48 | 52 |
| 15 | 49 | 51 |
| 16 | 49 | 51 |
| 17 | 49 | 51 |
| 18 | 49 | 51 |
| 19 | 49 | 51 |
| 20 | 49 | 51 |
| 21 | 49 | 51 |
| 22 | 49 | 51 |
| 23 | 48 | 52 |
| 24 | 49 | 51 |
| 25 | 48 | 52 |
| 26 | 48 | 52 |
| 27 | 48 | 52 |
| 28 | 49 | 51 |
| 29 | 49 | 51 |
| 30 | 48 | 52 |
| 31 | 48 | 52 |
Chance of precipitation in August
Isumi gets around 100 mm of rain over 11 wet days in August, the driest month. The line is the day-by-day chance of measurable precipitation.
Day to day, the chance of measurable rain averages around 37% and peaks near 45% on the wettest days. The odds climb toward the end of the month.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain chance (%) | 30 | 30 | 30 | 30 | 31 | 31 | 31 | 32 | 32 | 33 | 33 | 34 | 35 | 35 | 36 | 37 | 37 | 38 | 38 | 38 | 39 | 39 | 40 | 41 | 41 | 42 | 43 | 43 | 44 | 44 | 45 |
| Rain chance (%) | |
|---|---|
| 1 | 30 |
| 2 | 30 |
| 3 | 30 |
| 4 | 30 |
| 5 | 31 |
| 6 | 31 |
| 7 | 31 |
| 8 | 32 |
| 9 | 32 |
| 10 | 33 |
| 11 | 33 |
| 12 | 34 |
| 13 | 35 |
| 14 | 35 |
| 15 | 36 |
| 16 | 37 |
| 17 | 37 |
| 18 | 38 |
| 19 | 38 |
| 20 | 38 |
| 21 | 39 |
| 22 | 39 |
| 23 | 40 |
| 24 | 41 |
| 25 | 41 |
| 26 | 42 |
| 27 | 43 |
| 28 | 43 |
| 29 | 44 |
| 30 | 44 |
| 31 | 45 |
Humidity in August
Most of August feels miserable — the stacked bands show each day's mix of comfort levels, read off the dew point.
By dew point, August lands in the miserable band about 47% of days. Sticky, muggy-or-worse air turns up on roughly 97% of them.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Humid (%) | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 1 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| Muggy (%) | 8 | 8 | 7 | 7 | 7 | 8 | 8 | 8 | 8 | 8 | 8 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 10 | 10 | 10 | 11 | 12 | 12 | 13 | 14 | 15 | 16 |
| Oppressive (%) | 40 | 39 | 39 | 38 | 38 | 37 | 37 | 37 | 37 | 37 | 37 | 37 | 37 | 38 | 38 | 39 | 40 | 40 | 41 | 42 | 43 | 44 | 44 | 45 | 46 | 46 | 47 | 47 | 48 | 48 | 48 |
| Miserable (%) | 50 | 51 | 52 | 53 | 53 | 53 | 53 | 53 | 54 | 53 | 53 | 52 | 52 | 51 | 51 | 50 | 49 | 48 | 47 | 46 | 44 | 43 | 42 | 41 | 40 | 38 | 37 | 36 | 35 | 33 | 32 |
| Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|
| 1 | 2 | 8 | 40 | 50 |
| 2 | 2 | 8 | 39 | 51 |
| 3 | 2 | 7 | 39 | 52 |
| 4 | 2 | 7 | 38 | 53 |
| 5 | 2 | 7 | 38 | 53 |
| 6 | 2 | 8 | 37 | 53 |
| 7 | 2 | 8 | 37 | 53 |
| 8 | 2 | 8 | 37 | 53 |
| 9 | 1 | 8 | 37 | 54 |
| 10 | 2 | 8 | 37 | 53 |
| 11 | 2 | 8 | 37 | 53 |
| 12 | 2 | 9 | 37 | 52 |
| 13 | 2 | 9 | 37 | 52 |
| 14 | 2 | 9 | 38 | 51 |
| 15 | 2 | 9 | 38 | 51 |
| 16 | 2 | 9 | 39 | 50 |
| 17 | 2 | 9 | 40 | 49 |
| 18 | 3 | 9 | 40 | 48 |
| 19 | 3 | 9 | 41 | 47 |
| 20 | 3 | 9 | 42 | 46 |
| 21 | 3 | 9 | 43 | 44 |
| 22 | 3 | 10 | 44 | 43 |
| 23 | 3 | 10 | 44 | 42 |
| 24 | 3 | 10 | 45 | 41 |
| 25 | 3 | 11 | 46 | 40 |
| 26 | 3 | 12 | 46 | 38 |
| 27 | 3 | 12 | 47 | 37 |
| 28 | 3 | 13 | 47 | 36 |
| 29 | 3 | 14 | 48 | 35 |
| 30 | 3 | 15 | 48 | 33 |
| 31 | 3 | 16 | 48 | 32 |
Wind in August
Winds average 16 km/h in August, the calmest month.
Across August, daily wind ranges from about 16 km/h on the calmest days to 17 km/h at its breeziest. It stays fairly steady from day to day.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 16 | 16 | 16 | 16 | 16 | 16 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 16 | 16 | 16 | 16 | 16 | 16 | 17 | 17 | 17 | 17 |
| Feels | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze |
| Wind speed (km/h) | Feels | |
|---|---|---|
| 1 | 16 | light breeze |
| 2 | 16 | light breeze |
| 3 | 16 | light breeze |
| 4 | 16 | light breeze |
| 5 | 16 | light breeze |
| 6 | 16 | light breeze |
| 7 | 17 | light breeze |
| 8 | 17 | light breeze |
| 9 | 17 | light breeze |
| 10 | 17 | light breeze |
| 11 | 17 | light breeze |
| 12 | 17 | light breeze |
| 13 | 17 | light breeze |
| 14 | 17 | light breeze |
| 15 | 17 | light breeze |
| 16 | 17 | light breeze |
| 17 | 17 | light breeze |
| 18 | 17 | light breeze |
| 19 | 17 | light breeze |
| 20 | 17 | light breeze |
| 21 | 17 | light breeze |
| 22 | 16 | light breeze |
| 23 | 16 | light breeze |
| 24 | 16 | light breeze |
| 25 | 16 | light breeze |
| 26 | 16 | light breeze |
| 27 | 16 | light breeze |
| 28 | 17 | light breeze |
| 29 | 17 | light breeze |
| 30 | 17 | light breeze |
| 31 | 17 | light breeze |
Sunrise & sunset in August
Daylight runs from about 13 h 48 min at the start of August to 12 h 48 min by month's end. The lit band spans sunrise to sunset each day.
Days shrink by about 60 minutes over August. Sunrise moves from 4:51 AM to 5:14 AM, and sunset from 6:38 PM to 6:03 PM.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 13.8 | 13.8 | 13.7 | 13.7 | 13.7 | 13.7 | 13.6 | 13.6 | 13.6 | 13.5 | 13.5 | 13.5 | 13.4 | 13.4 | 13.4 | 13.3 | 13.3 | 13.3 | 13.2 | 13.2 | 13.2 | 13.1 | 13.1 | 13.1 | 13.0 | 13.0 | 13.0 | 12.9 | 12.9 | 12.9 | 12.8 |
| Sunrise (AM) | 4:51 | 4:51 | 4:52 | 4:53 | 4:54 | 4:55 | 4:55 | 4:56 | 4:57 | 4:58 | 4:58 | 4:59 | 5:00 | 5:01 | 5:02 | 5:02 | 5:03 | 5:04 | 5:05 | 5:05 | 5:06 | 5:07 | 5:08 | 5:09 | 5:09 | 5:10 | 5:11 | 5:12 | 5:12 | 5:13 | 5:14 |
| Sunset (PM) | 6:38 | 6:37 | 6:36 | 6:36 | 6:35 | 6:34 | 6:33 | 6:32 | 6:31 | 6:29 | 6:28 | 6:27 | 6:26 | 6:25 | 6:24 | 6:23 | 6:21 | 6:20 | 6:19 | 6:18 | 6:16 | 6:15 | 6:14 | 6:12 | 6:11 | 6:10 | 6:08 | 6:07 | 6:06 | 6:04 | 6:03 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| 1 | 13.8 | 4:51 | 6:38 |
| 2 | 13.8 | 4:51 | 6:37 |
| 3 | 13.7 | 4:52 | 6:36 |
| 4 | 13.7 | 4:53 | 6:36 |
| 5 | 13.7 | 4:54 | 6:35 |
| 6 | 13.7 | 4:55 | 6:34 |
| 7 | 13.6 | 4:55 | 6:33 |
| 8 | 13.6 | 4:56 | 6:32 |
| 9 | 13.6 | 4:57 | 6:31 |
| 10 | 13.5 | 4:58 | 6:29 |
| 11 | 13.5 | 4:58 | 6:28 |
| 12 | 13.5 | 4:59 | 6:27 |
| 13 | 13.4 | 5:00 | 6:26 |
| 14 | 13.4 | 5:01 | 6:25 |
| 15 | 13.4 | 5:02 | 6:24 |
| 16 | 13.3 | 5:02 | 6:23 |
| 17 | 13.3 | 5:03 | 6:21 |
| 18 | 13.3 | 5:04 | 6:20 |
| 19 | 13.2 | 5:05 | 6:19 |
| 20 | 13.2 | 5:05 | 6:18 |
| 21 | 13.2 | 5:06 | 6:16 |
| 22 | 13.1 | 5:07 | 6:15 |
| 23 | 13.1 | 5:08 | 6:14 |
| 24 | 13.1 | 5:09 | 6:12 |
| 25 | 13.0 | 5:09 | 6:11 |
| 26 | 13.0 | 5:10 | 6:10 |
| 27 | 13.0 | 5:11 | 6:08 |
| 28 | 12.9 | 5:12 | 6:07 |
| 29 | 12.9 | 5:12 | 6:06 |
| 30 | 12.9 | 5:13 | 6:04 |
| 31 | 12.8 | 5:14 | 6:03 |
Solar energy in August
Average shortwave solar energy reaching the ground each day in August, about 5.53 kWh/m² — the sunniest month for solar.
For context, solar energy here swings from a low near 2.25 kWh/m² to a high of 5.53 kWh/m² in August across the year — August's 5.53 kWh/m² sits near the top of that range.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 5.8 | 5.8 | 5.8 | 5.8 | 5.8 | 5.8 | 5.8 | 5.7 | 5.7 | 5.7 | 5.7 | 5.6 | 5.6 | 5.6 | 5.5 | 5.5 | 5.5 | 5.5 | 5.4 | 5.4 | 5.4 | 5.3 | 5.3 | 5.3 | 5.2 | 5.2 | 5.2 | 5.1 | 5.1 | 5.0 | 5.0 |
| Level | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| 1 | 5.8 | Bright |
| 2 | 5.8 | Bright |
| 3 | 5.8 | Bright |
| 4 | 5.8 | Bright |
| 5 | 5.8 | Bright |
| 6 | 5.8 | Bright |
| 7 | 5.8 | Bright |
| 8 | 5.7 | Bright |
| 9 | 5.7 | Bright |
| 10 | 5.7 | Bright |
| 11 | 5.7 | Bright |
| 12 | 5.6 | Bright |
| 13 | 5.6 | Bright |
| 14 | 5.6 | Bright |
| 15 | 5.5 | Bright |
| 16 | 5.5 | Bright |
| 17 | 5.5 | Bright |
| 18 | 5.5 | Bright |
| 19 | 5.4 | Bright |
| 20 | 5.4 | Bright |
| 21 | 5.4 | Bright |
| 22 | 5.3 | Bright |
| 23 | 5.3 | Bright |
| 24 | 5.3 | Bright |
| 25 | 5.2 | Bright |
| 26 | 5.2 | Bright |
| 27 | 5.2 | Bright |
| 28 | 5.1 | Bright |
| 29 | 5.1 | Bright |
| 30 | 5.0 | Bright |
| 31 | 5.0 | Bright |
Hazard calendar for Isumi
In August, Isumi sits inside its pacific typhoon season. The full year is below, with each hazard's peak months called out.
Isumi sits in the Pacific typhoon belt; the season peaks July–October.
Is August a good time to visit Isumi?
Our two travel scores rate August for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).
August is a reasonable time to visit Isumi for sightseeing. The water and warmth also suit a beach or pool day.
What to pack for Isumi in August
From August's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In August, Isumi sees daytime highs around 28°C and nights near 25°C. Pack light clothes. Worth having: rain gear and sun protection. About 11 days see rain.
Sea temperature near Isumi in August
The nearest coast averages about 26°C in August — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea offshore is warmest in August at about 26°C and coldest in February near 16°C.
It's comfortable for a long swim from May 22 to Dec 9 — about 6.6 months when the water holds above 20°C.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 18 | 16 | 16 | 18 | 20 | 22 | 24 | 26 | 26 | 24 | 22 | 20 |
| Comfort | Cool | Cool | Cool | Cool | Cool | Refreshing | Refreshing | Warm | Warm | Refreshing | Refreshing | Cool |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 18 | Cool |
| Feb | 16 | Cool |
| Mar | 16 | Cool |
| Apr | 18 | Cool |
| May | 20 | Cool |
| Jun | 22 | Refreshing |
| Jul | 24 | Refreshing |
| Aug | 26 | Warm |
| Sep | 26 | Warm |
| Oct | 24 | Refreshing |
| Nov | 22 | Refreshing |
| Dec | 20 | Cool |
UV index in Isumi in August
Clear-sky midday UV in August peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Isumi peaks around August 11 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 3 | 4 | 5 | 7 | 9 | 9 | 10 | 10 | 8 | 6 | 4 | 2 |
| Level | Moderate | Moderate | Moderate | High | Very high | Very high | Extreme | Extreme | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 3 | Moderate |
| Feb | 4 | Moderate |
| Mar | 5 | Moderate |
| Apr | 7 | High |
| May | 9 | Very high |
| Jun | 9 | Very high |
| Jul | 10 | Extreme |
| Aug | 10 | Extreme |
| Sep | 8 | Very high |
| Oct | 6 | High |
| Nov | 4 | Moderate |
| Dec | 2 | Moderate |
Air quality in Isumi in August
Average fine-particle pollution (PM2.5) through the year — so you can see where August falls, not just the annual average.
Air quality in Isumi is worst in April — around 22 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (September, 11 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 14 | 17 | 21 | 22 | 21 | 16 | 12 | 11 | 11 | 14 | 14 | 13 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 14 | Moderate |
| Feb | 17 | Moderate |
| Mar | 21 | Moderate |
| Apr | 22 | Moderate |
| May | 21 | Moderate |
| Jun | 16 | Moderate |
| Jul | 12 | Good |
| Aug | 11 | Good |
| Sep | 11 | Good |
| Oct | 14 | Moderate |
| Nov | 14 | Moderate |
| Dec | 13 | Moderate |
Where is Isumi?
Isumi sits at 35.2°N, 140.4°E, 1 m above sea level, in Japan. The nearest listed city is Ōhara, 2.0 km away.
Topography around Isumi
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Isumi.
Within 3 km, the terrain around Isumi has only modest variations in elevation — a maximum elevation change of 86 m around an average of 12 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 229 m; within 80 km, significant variations in elevation — a maximum elevation change of 396 m.
The land around Isumi is covered by water (59%) and trees (27%) within 3 km, water (62%) and trees (27%) within 16 km, and water (55%) and trees (21%) within 80 km.
Japan travel facts
- Travel advisory
- Level 1
- Exercise Normal Precautions
- Power plugs
- Type A / B
- 100 V · 50 / 60 Hz
- Prices
- ≈ 65% of US
- price level, 2025
- GDP per capita
- $35,951
- 2025
- Happiness
- 6.1 / 10
- World Happiness, 2025
- Safe drinking water
- 99%
- of population, 2024
- Homicide rate
- 0.2
- per 100k, 2023
- Road deaths
- 3.6
- per 100k/yr, 2019
- Income group
- High
- World Bank
- English
- Very low
- EF EPI 446
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Isumi (35.23°, 140.4049°, elevation 1 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).