Climate - San Juan (Argentina)

The climate of San Juan is arid subtropical, affected by altitude, with dry, mild winters (but during which it can get cold at night), and very hot, sunny summers. In addition, the climate is subject to sudden changes in temperature.
The city is located in north-central Argentina, at 31 degrees south latitude, and 650 meters (2,130 feet) above sea level.
Due to its location in a valley, with the Andes to the west and mountains to the north-east that exceed 3,000 meters (9,800 feet), the climate is particularly arid. However, thunderstorms can sometimes break out in the summer.
The sun often shines all year round.
In winter, from late May to mid-August, the difference in temperature between night and day is often noticeable, and, night frosts are quite frequent. During outbreaks cold air from the south, the temperature can drop to -5 °C (23 °F) or below at night and can remain around 8/10 °C (46/50 °F) during the day. In July 2011, it dropped to -9 °C (16 °F).
Since winter is dry, snow in San Juan is rare, however, light snowfalls may occur from time to time, such as in the months of July of 2000, 2007 and 2010.
On the other hand, the wind that comes down from the mountains, called Zonda and similar to the Föhn and the Chinook, is able to raise the temperature by several degrees, it is no coincidence that the heat records exceed 30 °C (86 °F) even in winter.
In spring, starting from mid-August, the temperature rises, and despite the altitude it can get very hot. Furthermore, in summer, from December to February, there can be heat waves, during which the temperature can sometimes reach 45 °C (113 °F). Even in summer, however, there can be outbursts of cool air from the south, perhaps accompanied by a thunderstorm, which can greatly lower the temperature for two or three days, so much so that at night it can be very cool even in midsummer.

Best Time

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It is difficult to find the best time to visit San Juan, as summer is very hot, while in winter there can be sudden changes in temperature, moreover, at night it is usually cold, and there can be quite intense frosts. You can then choose the period from mid-April to mid-May, when the temperature is halfway between winter and summer.

San Juan - Climate data

In San Juan, the average temperature of the coldest month (July) is of 8.5 °C (47.4 °F), that of the warmest month (January) is of 27.9 °C (82.1 °F). Here are the average temperatures.
In San Juan, precipitation amounts to 90 millimeters (3.5 inches) per year: it is therefore at a desert level. It ranges from 2 mm (0.1 in) in the driest month (June) to 20 mm (0.8 in) in the wettest one (February). Here is the average precipitation.
In San Juan, there are on average around 3365 sunshine hours per year. Here are the average hours of sunshine per day.

San Juan - Weather by month

Based on the period 1991-2020

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In January, the hottest month of the year, the weather in San Juan is usually very hot. However, there are remarkable differences between night and day. The average temperature is of 27.9 °C (82 °F), with a minimum of 19.7 °C (67.5 °F) and a maximum of 36 °C (96.8 °F).
On the coldest nights of the month, the temperature usually drops to around 13.5 °C (56 °F). However, it dropped to 9 °C (48.2 °F) in January 2019.
On the warmest days of the month, the temperature usually reaches around 41.5 °C (106.5 °F). However, it reached 45.4 °C (113.7 °F) in January 2003.
Precipitation amounts to 15 mm (0.6 in), distributed over 4 days.
The day lasts on average 13 hours and 55 minutes.
There are on average 11 hours of sunshine per day. So, the sun shines 78% of the time.
The average humidity is 40%.
The average wind speed is 16 kph (10 mph).

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In February, the weather in San Juan is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 26.3 °C (79 °F), with a minimum of 18.4 °C (65.1 °F) and a maximum of 34.1 °C (93.5 °F).
On the coldest nights of the month, the temperature usually drops to around 12 °C (53.5 °F). However, it dropped to 8.1 °C (46.6 °F) in February 2003.
On the warmest days of the month, the temperature usually reaches around 40 °C (103.5 °F). However, it reached 44.6 °C (112.3 °F) in February 2001.
Precipitation amounts to 20 mm (0.8 in), distributed over 3 days.
The day lasts on average 13 hours and 10 minutes.
There are on average 10.5 hours of sunshine per day. So, the sun shines 80% of the time.
The average humidity is 44%.
The average wind speed is 15 kph (9 mph).

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In March, the weather in San Juan is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 23.8 °C (75 °F), with a minimum of 16.1 °C (60.9 °F) and a maximum of 31.5 °C (88.6 °F).
On the coldest nights, the temperature usually drops to around 9.5 °C (49 °F). However, it dropped to 5.6 °C (42.1 °F) in March 1995.
On the warmest days, the temperature usually reaches around 37.5 °C (99.5 °F). However, it reached 42.1 °C (107.8 °F) in March 2002.
Precipitation amounts to 11 mm (0.4 in), distributed over 2 days.
The day lasts on average 12 hours and 10 minutes.
There are on average 9 hours of sunshine per day. So, the sun shines 75% of the time.
The average humidity is 49%.
The average wind speed is 13 kph (8 mph).

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In April, the weather in San Juan is usually warm. However, there are remarkable differences between night and day. The average temperature is of 18.5 °C (65 °F), with a minimum of 10.8 °C (51.4 °F) and a maximum of 26.2 °C (79.1 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 4 °C (39.5 °F). However, it dropped to -1.6 °C (29.1 °F) in April 2012.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 32.5 °C (91 °F). However, it reached 39.3 °C (102.7 °F) in April 2002.
Precipitation amounts to only 4 mm (0.2 in), and all occurs in one day.
The day lasts on average 11 hours and 20 minutes.
There are on average 9 hours of sunshine per day. So, the sun shines 80% of the time.
The average humidity is 53%.
The average wind speed is 12 kph (7 mph).

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In May, the weather in San Juan is usually mild. However, there are remarkable differences between night and day. The average temperature is of 13.4 °C (56 °F), with a minimum of 5.5 °C (42 °F) and a maximum of 21.2 °C (70.1 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -0.5 °C (31 °F). However, it dropped to -4.1 °C (24.6 °F) in May 1993.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 28 °C (83 °F). However, it reached 37.4 °C (99.3 °F) in May 1997.
Precipitation amounts to only 4 mm (0.2 in), and all occurs in one day.
The day lasts on average 10 hours and 30 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 71% of the time.
The average humidity is 58%.
The average wind speed is 9 kph (6 mph).

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In June, the weather in San Juan is usually mild. However, there are remarkable differences between night and day. The average temperature is of 9.4 °C (49 °F), with a minimum of 0.9 °C (33.6 °F) and a maximum of 17.9 °C (64.2 °F).
On the coldest nights, the temperature usually drops to around -4.5 °C (24 °F). However, it dropped to -7.5 °C (18.5 °F) in June 2011.
On the warmest days, the temperature usually reaches around 26.5 °C (79.5 °F). However, it reached 35 °C (95 °F) in June 2015.
Precipitation amounts to only 2 mm (0.1 in), distributed over 0 days.
The day lasts on average 10 hours and 5 minutes. June 21, the winter solstice, is the shortest day of the year in the Southern Hemisphere.
There are on average 7 hours of sunshine per day. So, the sun shines 68% of the time.
The average humidity is 55%.
The average wind speed is 10 kph (6 mph).

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In July, the coldest month of the year, the weather in San Juan is usually quite mild. However, there are remarkable differences between night and day. The average temperature is of 8.5 °C (47 °F), with a minimum of -0.3 °C (31.4 °F) and a maximum of 17.4 °C (63.3 °F).
On the coldest nights of the month, the temperature usually drops to around -5.5 °C (22 °F). However, it dropped to -9 °C (15.8 °F) in July 2011.
On the warmest days of the month, the temperature usually reaches around 26 °C (79 °F). However, it reached 33.4 °C (92.1 °F) in July 2006.
Precipitation amounts to only 4 mm (0.2 in), and all occurs in one day.
The day lasts on average 10 hours and 20 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 75% of the time.
The average humidity is 50%.
The average wind speed is 10 kph (6 mph).

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In August, the weather in San Juan is usually mild. However, there are remarkable differences between night and day. The average temperature is of 11.6 °C (53 °F), with a minimum of 2.3 °C (36.1 °F) and a maximum of 21 °C (69.9 °F).
On the coldest nights of the month, the temperature usually drops to around -3.5 °C (25.5 °F). However, it dropped to -7.2 °C (19 °F) in August 1991.
On the warmest days of the month, the temperature usually reaches around 31 °C (87.5 °F). However, it reached 38.5 °C (101.3 °F) in August 2015.
Precipitation amounts to only 3 mm (0.1 in), and all occurs in one day.
The day lasts on average 11 hours and 0 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 75% of the time.
The average humidity is 40%.
The average wind speed is 12 kph (7 mph).

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In September, the weather in San Juan is usually very mild. However, there are remarkable differences between night and day. The average temperature is of 15.6 °C (60 °F), with a minimum of 6.5 °C (43.8 °F) and a maximum of 24.7 °C (76.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -0.5 °C (31 °F). However, it dropped to -4.1 °C (24.6 °F) in September 2013.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 34 °C (93.5 °F). However, it reached 40.8 °C (105.4 °F) in September 2013.
Precipitation amounts to only 6 mm (0.2 in), distributed over 2 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 9 hours of sunshine per day. So, the sun shines 73% of the time.
The average humidity is 36%.
The average wind speed is 14 kph (9 mph).

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In October, the weather in San Juan is usually warm. However, there are remarkable differences between night and day. The average temperature is of 20.2 °C (68 °F), with a minimum of 11.3 °C (52.4 °F) and a maximum of 29 °C (84.3 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 4 °C (39 °F). However, it dropped to 1 °C (33.8 °F) in October 1991.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 37 °C (99 °F). However, it reached 42.5 °C (108.5 °F) in October 2009.
Precipitation amounts to only 4 mm (0.2 in), and all occurs in one day.
The day lasts on average 12 hours and 55 minutes.
There are on average 10 hours of sunshine per day. So, the sun shines 76% of the time.
The average humidity is 36%.
The average wind speed is 16 kph (10 mph).

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In November, the weather in San Juan is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 23.8 °C (75 °F), with a minimum of 14.9 °C (58.9 °F) and a maximum of 32.6 °C (90.7 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 7.5 °C (45 °F). However, it dropped to 2.5 °C (36.5 °F) in November 2014.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 39.5 °C (103 °F). However, it reached 44.5 °C (112.1 °F) in November 2009.
Precipitation amounts to only 7 mm (0.3 in), distributed over 2 days.
The day lasts on average 13 hours and 50 minutes.
There are on average 11 hours of sunshine per day. So, the sun shines 78% of the time.
The average humidity is 35%.
The average wind speed is 17 kph (11 mph).

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In December, the weather in San Juan is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 26.6 °C (80 °F), with a minimum of 18 °C (64.4 °F) and a maximum of 35.2 °C (95.3 °F).
On the coldest nights of the month, the temperature usually drops to around 10.5 °C (51 °F). However, it dropped to 6 °C (42.8 °F) in December 2014.
On the warmest days of the month, the temperature usually reaches around 41.5 °C (106.5 °F). However, it reached 45.7 °C (114.3 °F) in December 1995.
Precipitation amounts to 12 mm (0.5 in), distributed over 2 days.
The day lasts on average 14 hours and 10 minutes. So the days are long. December 21, the summer solstice, is the longest day of the year in the Southern Hemisphere.
There are on average 11.5 hours of sunshine per day. So, the sun shines 80% of the time.
The average humidity is 36%.
The average wind speed is 17 kph (11 mph).