Climate Insights for Isahaya

Isahaya Shi, Nagasaki Prefecture, Japan

Hottest
August
29°C peak
Coldest
January
7°C low
Wettest
June
419mm rain
Best to Visit
Varies throughout year

Climate Overview

The climate in Isahaya is temperate. The average annual temperature is 18°C and approximately 2289mm of precipitation falls per year. Isahaya receives a notable amount of rainfall throughout the year, including during its driest month. Isahaya is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: August, July, September. The coldest months are January, February, December, when temperatures can drop to 7°C.

Temperature

10° 15° 20° 25° 30° Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Max: 10° Average: 8° Min: 7° Feb Max: 11° Average: 9° Min: 7° Mar Max: 14° Average: 12° Min: 10° Apr Max: 18° Average: 16° Min: 14° May Max: 21° Average: 19° Min: 17° Jun Max: 24° Average: 22° Min: 21° Jul Max: 28° Average: 26° Min: 25° Aug Max: 29° Average: 28° Min: 26° Sep Max: 27° Average: 25° Min: 23° Oct Max: 22° Average: 20° Min: 18° Nov Max: 18° Average: 16° Min: 14° Dec Max: 12° Average: 10° Min: 8°
Max
Average
Min

Temperatures in Isahaya vary considerably across the year, with a 22°C difference between the coldest and warmest months. The warmest month is August, when average highs reach 29°C and the mean temperature sits around 28°C. January is the coolest month, with minimum temperatures around 7°C and an average of 8°C. Daily temperature variation is modest, with an average difference of 4°C between highs and lows. The sharpest temperature change occurs between November and December, with a 5°C shift in average temperatures.

Precipitation

0mm 50mm 100mm 150mm 200mm 250mm 300mm 350mm 400mm 450mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Precipitation: 84mm Snow: 1mm Feb Precipitation: 111mm Snow: 1mm Mar Precipitation: 147mm Snow: 0mm Apr Precipitation: 165mm Snow: 0mm May Precipitation: 235mm Snow: 0mm Jun Precipitation: 419mm Snow: 0mm Jul Precipitation: 356mm Snow: 0mm Aug Precipitation: 262mm Snow: 0mm Sep Precipitation: 210mm Snow: 0mm Oct Precipitation: 105mm Snow: 0mm Nov Precipitation: 109mm Snow: 0mm Dec Precipitation: 86mm Snow: 0mm
Precipitation
Snow

Isahaya is a very wet location, receiving approximately 2289mm of precipitation annually, which averages out to around 191mm per month. The wettest month is June, averaging 419mm of rainfall. July and August also tend to see above-average precipitation. The driest month is January, with just 84mm. That's 335mm less than June, the wettest month. Precipitation varies noticeably between seasons, with the first half (January to June) of the year generally seeing more rainfall.

Wind

0km/h 5km/h 10km/h 15km/h 20km/h 25km/h Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Wind Speed: 25km/h Feb Wind Speed: 24km/h Mar Wind Speed: 23km/h Apr Wind Speed: 22km/h May Wind Speed: 19km/h Jun Wind Speed: 19km/h Jul Wind Speed: 20km/h Aug Wind Speed: 20km/h Sep Wind Speed: 20km/h Oct Wind Speed: 21km/h Nov Wind Speed: 21km/h Dec Wind Speed: 24km/h
Wind Speed

Isahaya is moderately windy, with an average annual wind speed of 21km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is January, averaging 25km/h, noticeable enough to affect lighter outdoor activities. The calmest conditions occur in June, with average winds dropping to 19km/h, making it an ideal period for wind-sensitive activities. Wind conditions are fairly consistent throughout the year, varying by only 6km/h between the calmest and windiest months. Wind tends to be stronger during winter months, driven by seasonal pressure systems. The seasonal averages break down to 24km/h in winter, 21km/h in spring, 19km/h in summer, 21km/h in autumn.

Seasons

Winter
Dec 21
Spring
Mar 20
Summer
Jun 21
Autumn
Sep 23

89 days until Summer

It is currently spring in Isahaya, which began on March 20, 2026. Isahaya is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in August at around 29°C, while the coldest stretch bottoms out in January near 7°C. Summer is next, beginning on June 21, 2026 — 89 days from now.

Spring

Temperatures range from 10 to 21°C. Rainfall is heavy, totalling around 547mm across the season with a monthly average of 182mm. Winds are moderate at around 21km/h. An umbrella or waterproof jacket is advisable as spring showers are frequent.

Summer

Temperatures range from 21 to 29°C. Rainfall is heavy, totalling around 1037mm across the season with a monthly average of 346mm. Winds are moderate at around 19km/h. Light, breathable clothing is ideal — perfect conditions for outdoor activities.

Autumn

Temperatures range from 14 to 27°C. Rainfall is heavy, totalling around 424mm across the season with a monthly average of 141mm. Winds are moderate at around 21km/h. A waterproof jacket and sturdy footwear are recommended as rain becomes more frequent.

Winter

Temperatures range from 7 to 12°C. Precipitation is moderate at around 281mm for the season, averaging 94mm per month. Winds are moderate at around 24km/h. A light jacket or sweater is usually sufficient, though cooler evenings may call for an extra layer.

Monthly Climate Data

The table below shows monthly climate averages for Isahaya based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.

Month
Min Temperature
Max Temperature
Wind Speed
Precipitation
Snow
Jan
7 °C
10 °C
25 km/h
84 mm
1 cm
Feb
7 °C
11 °C
24 km/h
111 mm
1 cm
Mar Current
10 °C
14 °C
23 km/h
147 mm
0 cm
Apr
14 °C
18 °C
22 km/h
165 mm
0 cm
May
17 °C
21 °C
19 km/h
235 mm
0 cm
Jun
21 °C
24 °C
19 km/h
419 mm
0 cm
Jul
25 °C
28 °C
20 km/h
356 mm
0 cm
Aug
26 °C
29 °C
20 km/h
262 mm
0 cm
Sep
23 °C
27 °C
20 km/h
210 mm
0 cm
Oct
18 °C
22 °C
21 km/h
105 mm
0 cm
Nov
14 °C
18 °C
21 km/h
109 mm
0 cm
Dec
8 °C
12 °C
24 km/h
86 mm
0 cm
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Metric (°C, km/h)