Climate - San Bernardino (California)

The climate of San Bernardino is subtropical, with mild, relatively rainy winters and very hot, sunny summers.
The city is located 90 km (55 mi) east of Los Angeles, at an altitude of 300 meters (1,000 feet). Just to the north, we find the San Bernardino Mountains, where the San Bernardino National Forest is located, while to the south-west we find the Santa Ana Mountains, which isolate the area from the ocean, making it hotter in summer. In winter, however, sometimes at night it can be cold, and the temperature usually reaches -1/-3 °C (27/30 °F) on colder nights.
Due to its location in an area surrounded by mountains, the city is also subject to air stagnation and therefore pollution. In summer, the days are often scorching, although the highest temperatures are recorded when the Santa Ana wind blows from the desert. On the hottest days of the year, the temperature usually reaches 42/43 °C (108/109 °F). In July 2018, it reached 48 °C (118.5 °F).
The average temperature of the coldest month (December) is of 12.5 °C (54.5 °F), that of the warmest month (August) is of 27.5 °C (81.4 °F). Here are the average temperatures.

Precipitation amounts to 405 millimeters (15.9 inches) per year: it is therefore quite scarce (although in winter there may be periods of bad weather). It ranges from 0 mm (0 in) in the driest months (June, July) to 105 mm (4.1 in) in the wettest (February). Here is the average precipitation.

Best Time

To visit San Bernardino, you can choose the periods from mid-March to mid-April and from mid-October to mid-November. In winter, the weather is often mild and sunny, but sometimes it can be cold at night, and it can also rain.

Back to California.

San Bernardino - Weather by month

Based on the period 2009-2020

---

In January, the weather in San Bernardino is usually mild. However, there are remarkable differences between night and day. The average temperature is of 12.9 °C (55 °F), with a minimum of 5.9 °C (42.7 °F) and a maximum of 19.9 °C (67.7 °F).
On the coldest nights of the month, the temperature usually drops to around 0 °C (32 °F).
On the warmest days of the month, the temperature usually reaches around 27 °C (80.5 °F).
Precipitation amounts to 80 mm (3.1 in), distributed over 6 days.
The day lasts on average 10 hours and 10 minutes.
The average humidity is 45%.
The average wind speed is 5 kph (3 mph).

---

In February, the weather in San Bernardino is usually mild. However, there are remarkable differences between night and day. The average temperature is of 13.7 °C (57 °F), with a minimum of 7 °C (44.5 °F) and a maximum of 20.4 °C (68.8 °F).
On the coldest nights of the month, the temperature usually drops to around 1.5 °C (35 °F).
On the warmest days of the month, the temperature usually reaches around 27.5 °C (81.5 °F).
Precipitation amounts to 105 mm (4.1 in), distributed over 7 days.
The day lasts on average 11 hours and 0 minutes.
The average humidity is 46%.
The average wind speed is 6 kph (4 mph).

---

In March, the weather in San Bernardino is usually very mild. However, there are remarkable differences between night and day. The average temperature is of 15.4 °C (60 °F), with a minimum of 8.7 °C (47.7 °F) and a maximum of 22 °C (71.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 4 °C (39 °F).
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 30 °C (86 °F).
Precipitation amounts to 65 mm (2.6 in), distributed over 7 days.
The day lasts on average 12 hours and 0 minutes.
The average humidity is 49%.
The average wind speed is 7 kph (4 mph).

---

In April, the weather in San Bernardino is usually warm. However, there are remarkable differences between night and day. The average temperature is of 18.2 °C (65 °F), with a minimum of 10.8 °C (51.4 °F) and a maximum of 25.5 °C (78 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 5.5 °C (42 °F).
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 34 °C (93.5 °F).
Precipitation amounts to 25 mm (1 in), distributed over 3 days.
The day lasts on average 13 hours and 5 minutes.
The average humidity is 43%.
The average wind speed is 8 kph (5 mph).

---

In May, the weather in San Bernardino is usually warm. However, there are remarkable differences between night and day. The average temperature is of 20.5 °C (69 °F), with a minimum of 13.4 °C (56.1 °F) and a maximum of 27.6 °C (81.6 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 9 °C (48 °F).
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 35.5 °C (96 °F).
Precipitation amounts to only 5 mm (0.2 in), distributed over 2 days.
The day lasts on average 14 hours and 0 minutes.
The average humidity is 46%.
The average wind speed is 9 kph (5 mph).

---

In June, the weather in San Bernardino is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 23.9 °C (75 °F), with a minimum of 15.9 °C (60.5 °F) and a maximum of 32 °C (89.5 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 12.5 °C (54.5 °F).
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 39 °C (102.5 °F).
Precipitation amounts to only 0 mm (0 in), so on average it never rains in the whole month.
The day lasts on average 14 hours and 25 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
The average humidity is 43%.
The average wind speed is 9 kph (5 mph).

---

In July, the weather in San Bernardino is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 26.9 °C (80 °F), with a minimum of 18.8 °C (65.8 °F) and a maximum of 35.1 °C (95.1 °F).
On the coldest nights of the month, the temperature usually drops to around 14.5 °C (58.5 °F).
On the warmest days of the month, the temperature usually reaches around 41 °C (106 °F).
Precipitation amounts to only 0 mm (0 in), so on average it never rains in the whole month.
The day lasts on average 14 hours and 5 minutes. So the days are long.
The average humidity is 40%.
The average wind speed is 9 kph (5 mph).

---

In August, the warmest month of the year, the weather in San Bernardino is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 27.5 °C (81 °F), with a minimum of 18.8 °C (65.9 °F) and a maximum of 36.1 °C (96.9 °F).
On the coldest nights of the month, the temperature usually drops to around 14.5 °C (58 °F).
On the warmest days of the month, the temperature usually reaches around 42 °C (107.5 °F).
Precipitation amounts to only 5 mm (0.2 in), and all occurs in one day.
The day lasts on average 13 hours and 20 minutes.
The average humidity is 37%.
The average wind speed is 8 kph (5 mph).

---

In September, the weather in San Bernardino is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 25.9 °C (79 °F), with a minimum of 17.4 °C (63.4 °F) and a maximum of 34.4 °C (93.9 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 11.5 °C (53 °F).
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 41 °C (106 °F).
Precipitation amounts to only 5 mm (0.2 in), and all occurs in one day.
The day lasts on average 12 hours and 20 minutes.
The average humidity is 37%.
The average wind speed is 8 kph (5 mph).

---

In October, the weather in San Bernardino is usually warm. However, there are remarkable differences between night and day. The average temperature is of 21.2 °C (70 °F), with a minimum of 13.3 °C (56 °F) and a maximum of 29.1 °C (84.4 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 7.5 °C (46 °F).
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 37.5 °C (99.5 °F).
Precipitation amounts to 20 mm (0.8 in), distributed over 2 days.
The day lasts on average 11 hours and 20 minutes.
The average humidity is 39%.
The average wind speed is 7 kph (4 mph).

---

In November, the weather in San Bernardino is usually very mild. However, there are remarkable differences between night and day. The average temperature is of 16.3 °C (61 °F), with a minimum of 8.7 °C (47.6 °F) and a maximum of 23.9 °C (75 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 2.5 °C (37 °F).
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 33 °C (91 °F).
Precipitation amounts to 35 mm (1.4 in), distributed over 3 days.
The day lasts on average 10 hours and 25 minutes.
The average humidity is 37%.
The average wind speed is 5 kph (3 mph).

---

In December, the coldest month of the year, the weather in San Bernardino is usually mild. The average temperature is of 12.5 °C (54 °F), with a minimum of 6 °C (42.7 °F) and a maximum of 19 °C (66.2 °F).
On the coldest nights of the month, the temperature usually drops to around 0 °C (31.5 °F).
On the warmest days of the month, the temperature usually reaches around 26.5 °C (79.5 °F).
Precipitation amounts to 60 mm (2.4 in), distributed over 5 days.
The day lasts on average 9 hours and 55 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
The average humidity is 45%.
The average wind speed is 5 kph (3 mph).