Climate - Ontario (Oregon)

The climate of Ontario is arid continental, with cold winters and hot, sunny summers, and with strong temperature variations between night and day.
The city is located at 650 meters (2,100 ft) above sea level, in eastern Oregon. Across the Snake River is the city of Payette, in Idaho.
In winter, cold waves are possible, during which the temperature can drop to -20 °C (-4 °F) or even below. In January 2017, it dropped to -29 °C (-20 °F). Snowfalls are generally not abundant, given that the climate is arid. In an average year, 35 cm (13 in) of snow fall.
In summer there are strong temperature variations between night and day. During the day, it is often very hot, and sometimes the temperature can reach or exceed 40 °C (104 °F).
The average temperature of the coldest month (January) is of -0.4 °C (31.3 °F), that of the warmest month (July) is of 25.7 °C (78.3 °F). Here are the average temperatures.

Precipitation amounts to 240 millimeters (9.5 inches) per year: it is therefore scarce. It ranges from 5 mm (0.2 in) in the driest months (July, August, September) to 35 mm (1.4 in) in the wettest ones (January, December). Here is the average precipitation.

Best Time

To visit Ontario, you can choose the months of May and September. It is true that it rains a little more often than in summer (especially in May), and that it gets colder at night, but in this way, you can avoid the heat that can occur in summer. September is probably the best month.

Back to the climate of Oregon.

Ontario - Weather by month

Based on the period 1991-2020

---

In January, the coldest month of the year, the weather in Ontario is usually very cold. The average temperature is of -0.4 °C (31 °F), with a minimum of -4.3 °C (24.3 °F) and a maximum of 3.5 °C (38.3 °F).
On the coldest nights of the month, the temperature usually drops to around -14 °C (6.5 °F). However, it dropped to -28.9 °C (-20 °F) in January 2017.
On the warmest days of the month, the temperature usually reaches around 10 °C (50 °F). However, it reached 15 °C (59 °F) in January 2004.
Precipitation amounts to 35 mm (1.4 in), distributed over 10 days.
The day lasts on average 9 hours and 20 minutes.
The average humidity is 81%. Hence, the air is normally humid.
The average wind speed is 7 kph (4 mph).

---

In February, the weather in Ontario is usually cold. The average temperature is of 3.0 °C (37 °F), with a minimum of -2.2 °C (28 °F) and a maximum of 8.3 °C (46.9 °F).
On the coldest nights of the month, the temperature usually drops to around -10 °C (14 °F). However, it dropped to -13.3 °C (8.1 °F) in February 2004.
On the warmest days of the month, the temperature usually reaches around 14.5 °C (58 °F). However, it reached 19.4 °C (66.9 °F) in February 2015.
Precipitation amounts to 25 mm (1 in), distributed over 8 days.
The day lasts on average 10 hours and 30 minutes.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 9 kph (5 mph).

---

In March, the weather in Ontario is usually quite mild. However, there are remarkable differences between night and day. The average temperature is of 7.9 °C (46 °F), with a minimum of 1.1 °C (33.9 °F) and a maximum of 14.7 °C (58.4 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -6.5 °C (20.5 °F). However, it dropped to -10.6 °C (12.9 °F) in March 2002.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21.5 °C (70.5 °F). However, it reached 27.2 °C (81 °F) in March 2004.
Precipitation amounts to 25 mm (1 in), distributed over 10 days.
The day lasts on average 12 hours and 0 minutes.
The average humidity is 59%.
The average wind speed is 10 kph (6 mph).

---

In April, the weather in Ontario is usually mild. However, there are remarkable differences between night and day. The average temperature is of 11.5 °C (53 °F), with a minimum of 4.1 °C (39.4 °F) and a maximum of 18.9 °C (66 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -4 °C (24.5 °F). However, it dropped to -7.2 °C (19 °F) in April 2008.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 27 °C (81 °F). However, it reached 32.2 °C (90 °F) in April 2012.
Precipitation amounts to 20 mm (0.8 in), distributed over 7 days.
The day lasts on average 13 hours and 30 minutes.
The average humidity is 50%.
The average wind speed is 12 kph (8 mph).

---

In May, the weather in Ontario is usually very mild. However, there are remarkable differences between night and day. The average temperature is of 16.8 °C (62 °F), with a minimum of 8.8 °C (47.9 °F) and a maximum of 24.7 °C (76.4 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 0 °C (32.5 °F). However, it dropped to -3.3 °C (26.1 °F) in May 2002.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 33 °C (91.5 °F). However, it reached 37.8 °C (100 °F) in May 2003.
Precipitation amounts to 30 mm (1.2 in), distributed over 8 days.
The day lasts on average 14 hours and 50 minutes. So the days are long.
The average humidity is 47%.
The average wind speed is 11 kph (7 mph).

---

In June, the weather in Ontario is usually warm. However, there are remarkable differences between night and day. The average temperature is of 21 °C (70 °F), with a minimum of 12.7 °C (54.9 °F) and a maximum of 29.3 °C (84.7 °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). However, it dropped to 2.2 °C (36 °F) in June 2000.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 36.5 °C (98 °F). However, it reached 42.8 °C (109 °F) in June 2015.
Precipitation amounts to 20 mm (0.8 in), distributed over 6 days.
The day lasts on average 15 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 41%.
The average wind speed is 11 kph (7 mph).

---

In July, the hottest month of the year, the weather in Ontario is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 25.7 °C (78 °F), with a minimum of 16.4 °C (61.5 °F) and a maximum of 35.1 °C (95.1 °F).
On the coldest nights of the month, the temperature usually drops to around 10 °C (50 °F). However, it dropped to 6 °C (42.8 °F) in July 1999.
On the warmest days of the month, the temperature usually reaches around 40 °C (104.5 °F). However, it reached 44.4 °C (111.9 °F) in July 2002.
Precipitation amounts to only 5 mm (0.2 in), distributed over 2 days.
The day lasts on average 15 hours and 5 minutes. So the days are long.
The average humidity is 34%. Hence, the air is normally dry.
The average wind speed is 10 kph (6 mph).

---

In August, the weather in Ontario is usually warm to hot. However, there are remarkable differences between night and day. The average temperature is of 24.5 °C (76 °F), with a minimum of 14.9 °C (58.9 °F) and a maximum of 34.1 °C (93.4 °F).
On the coldest nights of the month, the temperature usually drops to around 8 °C (46.5 °F). However, it dropped to 4 °C (39.2 °F) in August 1999.
On the warmest days of the month, the temperature usually reaches around 39 °C (102 °F). However, it reached 41.7 °C (107.1 °F) in August 2020.
Precipitation amounts to only 5 mm (0.2 in), distributed over 2 days.
The day lasts on average 13 hours and 55 minutes.
The average humidity is 37%.
The average wind speed is 8 kph (5 mph).

---

In September, the weather in Ontario is usually warm. However, there are remarkable differences between night and day. The average temperature is of 18.9 °C (66 °F), with a minimum of 9.6 °C (49.2 °F) and a maximum of 28.2 °C (82.7 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 2 °C (36 °F). However, it dropped to -2.8 °C (27 °F) in September 2000.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 35 °C (95 °F). However, it reached 38.3 °C (100.9 °F) in September 2019.
Precipitation amounts to only 5 mm (0.2 in), distributed over 3 days.
The day lasts on average 12 hours and 25 minutes.
The average humidity is 44%.
The average wind speed is 8 kph (5 mph).

---

In October, the weather in Ontario 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 3.7 °C (38.7 °F) and a maximum of 19.4 °C (66.9 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -4 °C (24.5 °F). However, it dropped to -12.8 °C (9 °F) in October 2019.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 27.5 °C (82 °F). However, it reached 33 °C (91.4 °F) in October 1997.
Precipitation amounts to 15 mm (0.6 in), distributed over 5 days.
The day lasts on average 10 hours and 55 minutes.
The average humidity is 56%.
The average wind speed is 8 kph (5 mph).

---

In November, the weather in Ontario is usually quite cold. The average temperature is of 4.2 °C (40 °F), with a minimum of -1.4 °C (29.5 °F) and a maximum of 9.9 °C (49.8 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -9 °C (16 °F). However, it dropped to -19.4 °C (-2.9 °F) in November 2014.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 18 °C (64.5 °F). However, it reached 23 °C (73.4 °F) in November 2006.
Precipitation amounts to 20 mm (0.8 in), distributed over 8 days.
The day lasts on average 9 hours and 35 minutes.
The average humidity is 70%. Hence, the air is normally humid.
The average wind speed is 7 kph (5 mph).

---

In December, the weather in Ontario is usually very cold. The average temperature is of -0.2 °C (32 °F), with a minimum of -4.2 °C (24.4 °F) and a maximum of 3.8 °C (38.9 °F).
On the coldest nights of the month, the temperature usually drops to around -12.5 °C (9 °F). However, it dropped to -25.6 °C (-14.1 °F) in December 2013.
On the warmest days of the month, the temperature usually reaches around 11 °C (52 °F). However, it reached 15.6 °C (60.1 °F) in December 2012.
Precipitation amounts to 35 mm (1.4 in), distributed over 11 days.
The day lasts on average 8 hours and 55 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
The average humidity is 79%. Hence, the air is normally humid.
The average wind speed is 7 kph (4 mph).