Karuizawa weather in August

In August, Karuizawa sees average daytime highs of 26°C and overnight lows near 19°C, with 240 mm of rain across 24.1 wet days and about 13.4 hours of daylight. It is the 1st-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 27°C in the first days to 25°C by the end. The sky is clear or mostly clear about 13% of the time in August, and the air most often feels muggy.

Daylight stretches from about 13 h 54 min at the start of August to 12 h 48 min by month's end. Set against the rest of the year, August is Karuizawa's 9th-clearest and 11th-windiest month. For the whole year in context, see Karuizawa's year-round climate.

Daytime high
26°
1st warmest
Overnight low
19°
12th coldest
Rainfall
240 mm
24.1 wet days
Daylight
13 h 24 min
5:08 AM – 6:31 PM
Cloud cover
72%
9th clearest
Wind
5 km/h
11th windiest
Solar energy
4.79 kWh/m²
Travel score
4.5
out of 10

Temperature in August

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 27°C in the first days to 25°C by the end.

A typical August day in Karuizawa reaches about 26°C in the afternoon and slips back to 19°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 22°C and 30°C. Set against its neighbours, August runs about 1°C warmer than July and about 4°C warmer than September.

15°20°25°30°35°151015202531
Avg high (°C)Avg low (°C)
12720
22720
32720
42720
52720
62720
72720
82720
92720
102720
112720
122720
132620
142620
152620
162620
172619
182619
192619
202619
212619
222619
232619
242519
252519
262519
272519
282519
292518
302518
312518

How August really feels in Karuizawa

Once humidity and wind are folded in, August averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

August sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Karuizawa weather by month

How August compares with the rest of the year at a glance. August is the 1st-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -4°597.46.59.80.0
Feb / -4°608.66.710.60.0
Mar / -1°11013.17.111.71.3
Apr14° / 12213.82.112.93.7
May19° / 10°16516.80.113.95.1
Jun21° / 15°25422.7014.44.3
Jul25° / 19°28224014.24.5
Aug26° / 19°24024.1013.44.5
Sep22° / 16°24120.6012.24.8
Oct17° / 19515.5011.14.7
Nov11° / 728.80.610.13.1
Dec / -1°497.64.49.60.6

Cloud cover in August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 13% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 18% of August, with mostly cloudy or overcast conditions the remaining 69%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13367
23367
33466
43466
53466
63466
73565
83466
93367
103268
113268
123169
133169
143169
153070
163070
172971
183070
192971
202971
212971
222971
232971
242971
252971
262971
272971
282872
292872
302872
312971

Chance of precipitation in August

Any precipitation

Karuizawa gets around 240 mm of rain over 24.1 wet days in August. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 77% and peaks near 78% on the wettest days.

0%20%40%60%80%151015202531
Rain chance (%)
176
276
376
476
576
676
776
876
976
1077
1177
1277
1377
1477
1577
1678
1778
1878
1978
2078
2178
2278
2378
2478
2578
2678
2778
2878
2978
3077
3177

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

Most of August feels muggy — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, August lands in the muggy band about 65% of days. Sticky, muggy-or-worse air turns up on roughly 70% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
10319735
20318745
30318736
40318736
50317746
60317746
70317746
80316756
90316756
100316756
110317746
120417736
131417726
141418725
151418725
161519705
171520695
181621675
191722655
201724644
211825624
221827604
231929574
241930564
2511032543
2611034523
2711135503
2811137493
2911238472
3011239452
3111341432

Wind in August

Winds average 5 km/h in August.

Across August, daily wind ranges from about 4 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (km/h)Feels
14calm
24calm
34calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm
315calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 13 h 54 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 66 minutes over August. Sunrise moves from 4:55 AM to 5:20 AM, and sunset from 6:48 PM to 6:11 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.94:556:48
213.84:566:47
313.84:576:46
413.84:586:45
513.84:596:44
613.74:596:43
713.75:006:42
813.75:016:41
913.65:026:40
1013.65:036:38
1113.65:046:37
1213.55:046:36
1313.55:056:35
1413.55:066:34
1513.45:076:33
1613.45:086:31
1713.45:096:30
1813.35:096:29
1913.35:106:28
2013.35:116:26
2113.25:126:25
2213.25:136:24
2313.15:136:22
2413.15:146:21
2513.15:156:20
2613.05:166:18
2713.05:176:17
2813.05:186:15
2912.95:186:14
3012.95:196:12
3112.85:206:11

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 4.79 kWh/m².

For context, solar energy here swings from a low near 2.51 kWh/m² to a high of 5.52 kWh/m² in May across the year — August's 4.79 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
15.1Bright
25.1Bright
35.1Bright
45.1Bright
55.1Bright
65.1Bright
75.1Bright
85.0Bright
95.0Bright
105.0Bright
115.0Bright
124.9Bright
134.9Bright
144.8Bright
154.8Bright
164.8Bright
174.7Bright
184.7Bright
194.7Bright
204.6Bright
214.6Bright
224.6Bright
234.5Bright
244.5Bright
254.5Bright
264.4Bright
274.4Bright
284.4Bright
294.3Bright
304.3Bright
314.3Bright
Planning a trip in August

Hazard calendar for Karuizawa

In seasonPeak

In August, Karuizawa sits inside its rainy season season. The full year is below, with each hazard's peak months called out.

Karuizawa's rainy season runs May–October, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is August a good time to visit Karuizawa?

Our two travel scores rate August for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

4.5
Sightseeing
4th-best month of the year
4.3
Beach & pool
1st-best month of the year

August is a reasonable time to visit Karuizawa for sightseeing.

What to pack for Karuizawa in August

From August's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In August, Karuizawa sees daytime highs around 26°C and nights near 19°C. Pack rain gear. Worth having: light clothes and sun protection. About 24 days see rain.

rain gearlight clothessun protection

UV index in Karuizawa in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 9 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Karuizawa peaks around July 18 at about 10 (very high) — 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.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJul 18UV 10Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar6High
Apr7High
May8Very high
Jun9Very high
Jul10Very high
Aug9Very high
Sep9Very high
Oct6High
Nov3Moderate
Dec2Moderate

Air quality in Karuizawa in August

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where August falls, not just the annual average.

Air quality in Karuizawa is worst in April — around 21 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (December, 10 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1821 µg/m³Dec 1810 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar19Moderate
Apr21Moderate
May20Moderate
Jun18Moderate
Jul15Moderate
Aug14Moderate
Sep13Moderate
Oct12Moderate
Nov11Good
Dec10Good
Location & terrain

Where is Karuizawa?

Karuizawa sits at 36.4°N, 138.6°E, 952 m above sea level, in Japan. The nearest listed city is Miyota, 11 km away.

Topography around Karuizawa

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Karuizawa.

Within 3 km, the terrain around Karuizawa has large variations in elevation — a maximum elevation change of 632 m around an average of 1,004 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,316 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,985 m.

The land around Karuizawa is covered by trees (86%) within 3 km, trees (86%) within 16 km, and trees (80%) within 80 km.

3 km
632 m
16 km
2,316 m
80 km
2,985 m
treesgrasslandcroplandartificial surfacesbare terrainwater
August weather nearby: Miyota 11 km · Komoro 18 km · Saku 20 km · Annaka 24 km · Tōmi 24 km · Tomioka 26 km · Ueda 32 km · Nakanojō 32 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
Shintoism 49%Buddhism 46%other 4%Christianity 1%

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 Karuizawa (36.35°, 138.6333°, elevation 952 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. 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).