Climate - Nagasaki (Japan)

The climate of Nagasaki, a Japanese city located on the west coast of Kyushu (the southernmost of the major Japanese islands), is temperate humid, with quite mild winters and hot, moist, and rainy summers. Like the rest of Japan, the city is affected by the monsoon circulation: in winter, the northwest cold currents will prevail, while in summer, they will be replaced by hot and humid currents of tropical origin.
The city is located at a low latitude (at the 32rd parallel), but close enough to the Asian continent to receive cold air masses in winter, which are able to lower the temperature to some extent.
In winter, the sky is often cloudy, as is common on the Japanese western side; there are fairly mild periods, with highs above 10 °C (50 °F), alternating with cold periods, with wind and rain, highs around 5/7 °C (41/45 °F) or less, and possible falls of sleet or snow. Snowfalls, however, are generally light, as are nocturnal frosts.
Summers are hot and humid; there can be periods of good weather, with maximum temperatures around 35 °C (95 °F), tropical nights and high humidity, but also periods of bad weather due to the summer monsoon. August is the hottest month, both because of the thermal inertia of the sea and because of the lower frequency of periods of bad weather.
Here are the average temperatures.

Rainfall is abundant, in fact, it amounts to 1,900 millimeters (75 inches) per year. Winter is the driest season, but only in quantity. The rainiest months are June and July, ie the first period of the rainy season (called Baiu), which is particularly intense in southern Japan, especially on the west coast where Nagasaki is located: sometimes, the rains can be torrential. In the southwest of Japan, autumn is a decent season, and already in October, it typically doesn't rain much.
Here is the average precipitation.

From June to October (but especially from August to early October), Nagasaki may be affected by typhoons, the tropical cyclones of Southeast Asia.
The cherry blossoming in Nagasaki occurs around March 31.
The amount of sunshine in Nagasaki is not very good, however, there are two relative maxima, one in spring (April-May), and the other in August, after the Baiu rains. In October too, after the summer rains, the amount of sunshine increases a little. Here are the average sunshine hours per day.



In winter, the sea in Nagasaki is cold but not impossible for the more daring; it is warm enough for swimming, with a temperature of 23 °C (73 °F) or more, from July to October, and it becomes pleasantly warm in August. Here are the average sea temperatures.

Nagasaki - Weather by month

Based on the period 1991-2020

---

In January, the coldest month of the year, the weather in Nagasaki is usually quite mild. The average temperature is of 7.1 °C (45 °F), with a minimum of 4.1 °C (39.4 °F) and a maximum of 10 °C (50 °F).
On the coldest nights of the month, the temperature usually drops to around -0.5 °C (31 °F). However, it dropped to -4 °C (24.8 °F) in January 2016.
On the warmest days of the month, the temperature usually reaches around 16 °C (61 °F). However, it reached 20 °C (68 °F) in January 2017.
Precipitation amounts to 65 mm (2.6 in), distributed over 10 days.
The day lasts on average 10 hours and 20 minutes.
There are on average 3.5 hours of sunshine per day. So, the sun shines 32% of the time.
The average humidity is 66%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 18.5 °C (65 °F). Therefore, the sea is very cool for swimming.

---

In February, the weather in Nagasaki is usually quite mild. The average temperature is of 7.9 °C (46 °F), with a minimum of 4.5 °C (40.1 °F) and a maximum of 11.3 °C (52.3 °F).
On the coldest nights of the month, the temperature usually drops to around 0 °C (32 °F). However, it dropped to -3 °C (26.6 °F) in February 2012.
On the warmest days of the month, the temperature usually reaches around 18 °C (64.5 °F). However, it reached 22 °C (71.6 °F) in February 2010.
Precipitation amounts to 85 mm (3.3 in), distributed over 10 days.
The day lasts on average 11 hours and 0 minutes.
There are on average 4 hours of sunshine per day. So, the sun shines 39% of the time.
The average humidity is 65%.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 17.5 °C (63.5 °F). Therefore, the sea is cold for swimming.

---

In March, the weather in Nagasaki is usually mild. The average temperature is of 11.1 °C (52 °F), with a minimum of 7.5 °C (45.4 °F) and a maximum of 14.6 °C (58.4 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 1.5 °C (35 °F). However, it dropped to 0 °C (32 °F) in March 2001.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21 °C (69.5 °F). However, it reached 24 °C (75.2 °F) in March 2007.
Precipitation amounts to 125 mm (4.9 in), distributed over 11 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 5 hours of sunshine per day. So, the sun shines 40% of the time.
The average humidity is 65%.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 17.5 °C (63.5 °F). Therefore, the sea is cold for swimming.

---

In April, the weather in Nagasaki is usually very mild. The average temperature is of 15.8 °C (60 °F), with a minimum of 12.1 °C (53.8 °F) and a maximum of 19.5 °C (67.1 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 6 °C (43 °F). However, it dropped to 3 °C (37.4 °F) in April 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 25 °C (77 °F). However, it reached 28 °C (82.4 °F) in April 1998.
Precipitation amounts to 155 mm (6.1 in), distributed over 10 days.
The day lasts on average 13 hours and 0 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 45% of the time.
The average humidity is 65%.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 18.5 °C (65.5 °F). Therefore, the sea is very cool for swimming.

---

In May, the weather in Nagasaki is usually warm. The average temperature is of 20.2 °C (68 °F), with a minimum of 16.6 °C (62 °F) and a maximum of 23.7 °C (74.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 12 °C (53 °F). However, it dropped to 9 °C (48.2 °F) in May 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 28.5 °C (83 °F). However, it reached 32 °C (89.6 °F) in May 2014.
Precipitation amounts to 160 mm (6.3 in), distributed over 10 days.
The day lasts on average 13 hours and 55 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 43% of the time.
The average humidity is 68%.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 20.5 °C (68.5 °F). Therefore, the sea is cool for swimming.

---

In June, the weather in Nagasaki is usually warm to hot and muggy. The average temperature is of 23.6 °C (75 °F), with a minimum of 20.9 °C (69.6 °F) and a maximum of 26.4 °C (79.6 °F).
On the coldest nights, the temperature usually drops to around 17 °C (62.5 °F). However, it dropped to 15 °C (59 °F) in June 1992.
On the warmest days, the temperature usually reaches around 30.5 °C (87 °F). However, it reached 36 °C (96.8 °F) in June 2004.
Precipitation amounts to 335 mm (13.2 in), distributed over 14 days.
The day lasts on average 14 hours and 20 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 4.5 hours of sunshine per day. So, the sun shines 31% of the time.
The average humidity is 77%. Hence, the air is normally humid.
The average wind speed is 12 kph (7 mph).
The average sea temperature is of 23 °C (73 °F). Therefore, the sea can be considered barely acceptable for swimming.

---

In July, the weather in Nagasaki is usually very hot and muggy. The average temperature is of 27.6 °C (82 °F), with a minimum of 24.9 °C (76.9 °F) and a maximum of 30.2 °C (86.4 °F).
On the coldest nights of the month, the temperature usually drops to around 21.5 °C (70.5 °F). However, it dropped to 19 °C (66.2 °F) in July 1999.
On the warmest days of the month, the temperature usually reaches around 34.5 °C (93.5 °F). However, it reached 37 °C (98.6 °F) in July 1994.
Precipitation amounts to 295 mm (11.6 in), distributed over 12 days.
The day lasts on average 14 hours and 0 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 41% of the time.
The average humidity is 77%. Hence, the air is normally humid.
The average wind speed is 12 kph (7 mph).
The average sea temperature is of 26 °C (79 °F). Therefore, the sea is warm enough for swimming.

---

In August, the warmest month of the year, the weather in Nagasaki is usually very hot and muggy. The average temperature is of 28.7 °C (84 °F), with a minimum of 25.6 °C (78 °F) and a maximum of 31.9 °C (89.4 °F).
On the coldest nights of the month, the temperature usually drops to around 22 °C (72 °F). However, it dropped to 20 °C (68 °F) in August 1991.
On the warmest days of the month, the temperature usually reaches around 35.5 °C (96 °F). However, it reached 39 °C (102.2 °F) in August 2013.
Precipitation amounts to 220 mm (8.7 in), distributed over 11 days.
The day lasts on average 13 hours and 20 minutes.
There are on average 7 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 28 °C (82.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

---

In September, the weather in Nagasaki is usually warm to hot and muggy. The average temperature is of 25.3 °C (78 °F), with a minimum of 22.1 °C (71.7 °F) and a maximum of 28.6 °C (83.4 °F).
On the coldest nights, the temperature usually drops to around 17.5 °C (63 °F). However, it dropped to 14 °C (57.2 °F) in September 1993.
On the warmest days, the temperature usually reaches around 33 °C (91 °F). However, it reached 35 °C (95 °F) in September 1998.
Precipitation amounts to 185 mm (7.3 in), distributed over 10 days.
The day lasts on average 12 hours and 20 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 47% of the time.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 27 °C (80.5 °F). Therefore, the sea is pleasantly warm and allows long swims.

---

In October, the weather in Nagasaki is usually warm. The average temperature is of 20.3 °C (69 °F), with a minimum of 16.9 °C (62.4 °F) and a maximum of 23.8 °C (74.8 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 11.5 °C (52.5 °F). However, it dropped to 7 °C (44.6 °F) in October 1997.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 28.5 °C (83.5 °F). However, it reached 32 °C (89.6 °F) in October 2005.
Precipitation amounts to 100 mm (3.9 in), distributed over 7 days.
The day lasts on average 11 hours and 20 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 52% of the time.
The average humidity is 65%.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 25 °C (77 °F). Therefore, the sea is warm enough for swimming.

---

In November, the weather in Nagasaki is usually very mild. The average temperature is of 14.7 °C (59 °F), with a minimum of 11.5 °C (52.7 °F) and a maximum of 18 °C (64.4 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 5 °C (41 °F). However, it dropped to 0.6 °C (33.1 °F) in November 1997.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 23 °C (73.5 °F). However, it reached 25 °C (77 °F) in November 1996.
Precipitation amounts to 100 mm (3.9 in), distributed over 10 days.
The day lasts on average 10 hours and 30 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 44% of the time.
The average humidity is 67%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 22.5 °C (73 °F). Therefore, the sea can be considered barely acceptable for swimming.

---

In December, the weather in Nagasaki is usually mild. The average temperature is of 9.5 °C (49 °F), with a minimum of 6.4 °C (43.6 °F) and a maximum of 12.5 °C (54.4 °F).
On the coldest nights of the month, the temperature usually drops to around 1.5 °C (34.5 °F). However, it dropped to -1 °C (30.2 °F) in December 2001.
On the warmest days of the month, the temperature usually reaches around 18 °C (64.5 °F). However, it reached 25 °C (77 °F) in December 2018.
Precipitation amounts to 75 mm (3 in), distributed over 10 days.
The day lasts on average 10 hours and 0 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 4 hours of sunshine per day. So, the sun shines 38% of the time.
The average humidity is 65%.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 20.5 °C (68.5 °F). Therefore, the sea is cool for swimming.