Kosai weather in April

In April, Kosai sees average daytime highs of 19°C and overnight lows near 11°C, with 151 mm of rain across 10.4 wet days and about 12.8 hours of daylight. It is the 7th-warmest and 6th-wettest month of the year here.

Highs climb over the month, from about 17°C in the first days to 21°C by the end. The sky is clear or mostly clear about 36% of the time in April, and the air most often feels dry.

Daylight stretches from about 12 h 18 min at the start of April to 13 h 18 min by month's end. Set against the rest of the year, April is Kosai's 7th-clearest and 5th-windiest month. For the whole year in context, see Kosai's year-round climate.

Daytime high
19°
7th warmest
Overnight low
11°
6th coldest
Rainfall
151 mm
10.4 wet days
Daylight
12 h 54 min
5:24 AM – 6:16 PM
Cloud cover
57%
7th clearest
Wind
15 km/h
5th windiest
Solar energy
5.15 kWh/m²
Travel score
6.0
out of 10

Kosai is city in Shizuoka Prefecture, Japan.

Density
691/km²
people per km²
Founded
1972

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in April

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 17°C in the first days to 21°C by the end.

A typical April day in Kosai reaches about 19°C in the afternoon and slips back to 11°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 15°C and 23°C. Set against its neighbours, April runs about 5°C warmer than March and about 4°C cooler than May.

10°15°20°25°151015202530
Avg high (°C)Avg low (°C)
1178
2178
3178
4178
5179
6189
7189
8189
9189
101810
111810
121910
131910
141910
151911
161911
171911
182011
192011
202011
212012
222012
232012
242012
252112
262112
272113
282113
292113
302113

How April really feels in Kosai

Once humidity and wind are folded in, April 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

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

Kosai weather by month

How April compares with the rest of the year at a glance. April is the 7th-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan10° / 655.89.92.6
Feb11° / 816.810.73.0
Mar14° / 13510.511.74.3
Apr19° / 11°15110.412.86.0
May23° / 15°17011.313.86.5
Jun26° / 20°24215.614.35.4
Jul30° / 24°25015.814.14.2
Aug31° / 25°14415.313.33.8
Sep28° / 22°23614.612.25.2
Oct23° / 16°21111.811.16.6
Nov18° / 10°1138.910.25.9
Dec12° / 676.39.73.9

Cloud cover in April

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 36% of the time in April.

Beyond those clear spells, partly cloudy skies cover about 13% of April, with mostly cloudy or overcast conditions the remaining 51%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15347
25347
35347
45347
55347
65248
75248
85248
95248
105149
115050
125050
134951
144951
154852
164852
174654
184753
194753
204753
214654
224654
234753
244654
254654
264654
274654
284555
294555
304555

Chance of precipitation in April

Any precipitation

Kosai gets around 151 mm of rain over 10.4 wet days in April. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 35% and peaks near 36% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
136
235
335
435
535
635
735
835
935
1035
1135
1235
1336
1436
1536
1636
1736
1836
1936
2036
2136
2236
2336
2435
2535
2635
2734
2834
2934
3034

Humidity in April

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, April lands in the dry band about 86% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
195410
295410
394510
494510
594510
693610
793610
893610
992710
1092710
1192710
1291810
1391810
1489821
1588921
1688921
17871021
18871021
19851131
20841231
21831331
22821431
23801541
24781741
25761851
26751951
27732061
28722161
29702271
30702271

Wind in April

Winds average 15 km/h in April.

Across April, daily wind ranges from about 14 km/h on the calmest days to 15 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
115light breeze
215light breeze
315light breeze
415light breeze
515light breeze
615light breeze
715light breeze
815light breeze
915light breeze
1015light breeze
1115light breeze
1215light breeze
1315light breeze
1415light breeze
1515light breeze
1614light breeze
1714light breeze
1814light breeze
1914light breeze
2014light breeze
2114light breeze
2214light breeze
2314light breeze
2414light breeze
2514light breeze
2614light breeze
2714light breeze
2814light breeze
2914light breeze
3014light breeze

Sunrise & sunset in April

DaylightNight

Daylight runs from about 12 h 18 min at the start of April to 13 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 60 minutes over April. Sunrise moves from 5:45 AM to 5:07 AM, and sunset from 6:04 PM to 6:28 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.35:456:04
212.45:436:05
312.45:426:06
412.45:416:07
512.55:396:07
612.55:386:08
712.55:366:09
812.65:356:10
912.65:346:11
1012.75:326:11
1112.75:316:12
1212.75:296:13
1312.85:286:14
1412.85:276:15
1512.85:256:15
1612.95:246:16
1712.95:236:17
1812.95:216:18
1913.05:206:19
2013.05:196:19
2113.05:186:20
2213.15:166:21
2313.15:156:22
2413.15:146:23
2513.25:136:23
2613.25:126:24
2713.25:106:25
2813.35:096:26
2913.35:086:27
3013.35:076:28

Solar energy in April

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in April, about 5.15 kWh/m².

For context, solar energy here swings from a low near 2.62 kWh/m² to a high of 5.4 kWh/m² in May across the year — April's 5.15 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
14.9Bright
24.9Bright
35.0Bright
45.0Bright
55.0Bright
65.0Bright
75.0Bright
85.0Bright
95.1Bright
105.1Bright
115.1Bright
125.1Bright
135.1Bright
145.1Bright
155.1Bright
165.1Bright
175.1Bright
185.1Bright
195.2Bright
205.2Bright
215.2Bright
225.2Bright
235.2Bright
245.2Bright
255.2Bright
265.3Bright
275.3Bright
285.3Bright
295.3Bright
305.3Bright
Planning a trip in April

Hazard calendar for Kosai

In seasonPeak

In April, Kosai sits inside its pacific typhoon season. The full year is below, with each hazard's peak months called out.

Kosai sits in the Pacific typhoon belt; the season peaks July–October.

Pacific typhoon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is April a good time to visit Kosai?

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

6.0
Sightseeing
3rd-best month of the year
2.7
Beach & pool
7th-best month of the year

April is a reasonable time to visit Kosai for sightseeing.

What to pack for Kosai in April

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

In April, Kosai sees daytime highs around 19°C and nights near 11°C. Worth packing: rain gear and sun protection. About 10 days see rain.

rain gearsun protection

Sea temperature near Kosai in April

The nearest coast averages about 17°C in April — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 13 km away) is warmest in August at about 27°C and coldest in February near 16°C.

It's comfortable for a long swim from May 25 to Nov 28 — about 6.2 months when the water holds above 20°C.

15°20°25°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan16Cool
Feb16Cool
Mar16Cool
Apr17Cool
May19Cool
Jun22Refreshing
Jul25Warm
Aug27Warm
Sep26Warm
Oct23Refreshing
Nov21Refreshing
Dec19Cool

UV index in Kosai in April

LowModerateHighVery highExtreme

Clear-sky midday UV in April peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Kosai peaks around July 15 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highModerateJul 15UV 10Dec 22UV 3
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5Moderate
Apr7High
May9Very high
Jun10Very high
Jul10Very high
Aug9Very high
Sep9Very high
Oct6High
Nov4Moderate
Dec3Moderate

Air quality in Kosai in April

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Kosai is worst in April — around 25 µg/m³ PM2.5 (moderate), about 1.6× the cleanest month (July, 15 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateApr 1325 µg/m³Jul 2415 µg/m³
PM2.5 (µg/m³)Level
Jan17Moderate
Feb19Moderate
Mar25Moderate
Apr25Moderate
May24Moderate
Jun20Moderate
Jul15Moderate
Aug15Moderate
Sep16Moderate
Oct18Moderate
Nov18Moderate
Dec16Moderate
Location & terrain

Where is Kosai?

Kosai sits at 34.7°N, 137.5°E, 30 m above sea level, in Japan. The nearest listed city is Arai, 4.0 km away.

Topography around Kosai

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

Within 3 km, the terrain around Kosai has only modest variations in elevation — a maximum elevation change of 83 m around an average of 33 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 463 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,300 m.

The land around Kosai is covered by trees (41%) and artificial surfaces (31%) within 3 km, water (47%) and trees (25%) within 16 km, and water (43%) and trees (42%) within 80 km.

3 km
83 m
16 km
463 m
80 km
2,300 m
treesgrasslandcroplandartificial surfacesbare terrainwater
April weather nearby: Arai 4.0 km · Toyohashi 15 km · Toyokawa 17 km · Kozakai-chō 19 km · Hamamatsu 19 km · Shinshiro 22 km · Tahara 24 km · Hamakita 26 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 Kosai (34.7005°, 137.5225°, elevation 30 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).