Weather and climate in Eureka (California)

The climate of Eureka is oceanic, with mild, rainy winters and cool, sunny summers.
The city is located in the extreme northwest of California, on Humboldt Bay, and a short distance from the border with Oregon.
The latitude is not very low (we are at the 40th parallel), so weather fronts from the ocean arrive in the cold half of the year.
In winter, the rains are abundant. The temperature can drop a few degrees below freezing on the coldest nights. Snow is very rare.
Summer is particularly cool because of the cold current flowing in the ocean. Besides, as mentioned, the summer is sunny, although there may be morning fogs. From May to October, the temperature can reach 28/30 °C (82/86 °F), generally for a day or two, when the wind blows from the desert, but given the distance, this happens very rarely.
North of the city is the Redwood National Park, where the tallest tree in the world, called Hyperion (whose exact location is secret though) is located.
The average temperature of the coldest month (December) is of 8.9 °C (48 °F), that of the warmest month (August) is of 14.4 °C (57.9 °F). Here are the average temperatures.

Precipitation amounts to 1,170 millimeters (46.1 inches) per year: it is therefore quite abundant. It ranges from 5 mm (0.2 in) in the driest months (July, August) to 225 mm (8.9 in) in the wettest (December). Here is the average precipitation.

On average, there are around 2,465 sunshine hours per year. The relatively sunniest season is spring, because in summer, even if it is the driest season, morning fogs can form. Here are the average sunshine hours per day.

The sea temperature ranges between 11 °C (52 °F) and 14 °C (57 °F). So, it is cold all year round. Here are the average sea temperatures.

Best Time

The best time to visit Eureka is from June to September, as it is the mildest and driest of the year.

Back to California.

Eureka - Weather by month

Based on the period 1991-2020

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January is generally a mild month. The average temperature is of 9.1 °C (48 °F), with a minimum of 4.7 °C (40.5 °F) and a maximum of 13.6 °C (56.4 °F).
On the coldest nights of the month, the temperature usually drops to around -1 °C (30 °F). However, it dropped to -5 °C (23 °F) in January 2007.
On the warmest days of the month, the temperature usually reaches around 20 °C (68 °F). However, it reached 24 °C (75.2 °F) in January 2003.
Precipitation amounts to 190 mm (7.5 in), distributed over 18 days.
The day lasts on average 9 hours and 35 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 47% of the time.
The average humidity is 83%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 11.5 °C (52.5 °F). Therefore, the sea is very cold for swimming.

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February is generally a mild month. The average temperature is of 9.2 °C (49 °F), with a minimum of 4.8 °C (40.6 °F) and a maximum of 13.7 °C (56.6 °F).
On the coldest nights of the month, the temperature usually drops to around -1 °C (30.5 °F). However, it dropped to -3.9 °C (25 °F) in February 2011.
On the warmest days of the month, the temperature usually reaches around 20.5 °C (68.5 °F). However, it reached 26.7 °C (80.1 °F) in February 2016.
Precipitation amounts to 165 mm (6.5 in), distributed over 18 days.
The day lasts on average 10 hours and 40 minutes.
There are on average 5 hours of sunshine per day. So, the sun shines 48% of the time.
The average humidity is 82%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 11 °C (52 °F). Therefore, the sea is very cold for swimming.

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March is generally a mild month. The average temperature is of 9.5 °C (49 °F), with a minimum of 5.2 °C (41.4 °F) and a maximum of 13.7 °C (56.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 0 °C (32 °F). However, it dropped to -2.2 °C (28 °F) in March 2008.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 19.5 °C (67 °F). However, it reached 23 °C (73.4 °F) in March 2000.
Precipitation amounts to 160 mm (6.3 in), distributed over 18 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 6.5 hours of sunshine per day. So, the sun shines 56% of the time.
The average humidity is 83%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 11 °C (52 °F). Therefore, the sea is very cold for swimming.

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April is generally a mild month. The average temperature is of 10.1 °C (50 °F), with a minimum of 6 °C (42.8 °F) and a maximum of 14.3 °C (57.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 0.5 °C (33 °F). However, it dropped to -2 °C (28.4 °F) in April 2009.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21 °C (70 °F). However, it reached 28.3 °C (82.9 °F) in April 2014.
Precipitation amounts to 105 mm (4.1 in), distributed over 14 days.
The day lasts on average 13 hours and 25 minutes.
There are on average 8.5 hours of sunshine per day. So, the sun shines 63% of the time.
The average humidity is 83%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 11 °C (52 °F). Therefore, the sea is very cold for swimming.

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May is generally a mild month. The average temperature is of 11.6 °C (53 °F), with a minimum of 7.8 °C (46 °F) and a maximum of 15.4 °C (59.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 3 °C (37 °F). However, it dropped to 0 °C (32 °F) in May 2002.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 22 °C (71 °F). However, it reached 34.4 °C (93.9 °F) in May 2008.
Precipitation amounts to 55 mm (2.2 in), distributed over 11 days.
The day lasts on average 14 hours and 30 minutes. So the days are long.
There are on average 9 hours of sunshine per day. So, the sun shines 62% of the time.
The average humidity is 85%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 11.5 °C (53 °F). Therefore, the sea is very cold for swimming.

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June is generally a mild month. The average temperature is of 13.1 °C (55 °F), with a minimum of 9.2 °C (48.5 °F) and a maximum of 16.9 °C (62.5 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 4.5 °C (40 °F). However, it dropped to 1.7 °C (35.1 °F) in June 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 22.5 °C (72 °F). However, it reached 28.9 °C (84 °F) in June 2019.
Precipitation amounts to 25 mm (1 in), distributed over 6 days.
The day lasts on average 15 hours and 5 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 9.5 hours of sunshine per day. So, the sun shines 61% of the time.
The average humidity is 85%. Hence, the air is normally humid.
The average wind speed is 11 kph (7 mph).
The average sea temperature is of 12.5 °C (54.5 °F). Therefore, the sea is very cold for swimming.

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July is generally a mild month. The average temperature is of 14.1 °C (57 °F), with a minimum of 10.7 °C (51.3 °F) and a maximum of 17.4 °C (63.4 °F).
On the coldest nights of the month, the temperature usually drops to around 7.5 °C (45 °F). However, it dropped to 5.5 °C (41.9 °F) in July 1993.
On the warmest days of the month, the temperature usually reaches around 21.5 °C (71 °F). However, it reached 28.9 °C (84 °F) in July 2015.
Precipitation amounts to only 5 mm (0.2 in), distributed over 5 days.
The day lasts on average 14 hours and 40 minutes. So the days are long.
There are on average 9 hours of sunshine per day. So, the sun shines 60% of the time.
The average humidity is 88%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 13 °C (55.5 °F). Therefore, the sea is very cold for swimming.

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August, the warmest month of the year, is generally a mild month. The average temperature is of 14.4 °C (58 °F), with a minimum of 10.7 °C (51.3 °F) and a maximum of 18.1 °C (64.5 °F).
On the coldest nights of the month, the temperature usually drops to around 7 °C (44.5 °F). However, it dropped to 5 °C (41 °F) in August 2002.
On the warmest days of the month, the temperature usually reaches around 23.5 °C (74 °F). However, it reached 30 °C (86 °F) in August 2008.
Precipitation amounts to only 5 mm (0.2 in), distributed over 6 days.
The day lasts on average 13 hours and 40 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 56% of the time.
The average humidity is 89%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 13.5 °C (56.5 °F). Therefore, the sea is very cold for swimming.

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September is generally a mild month. The average temperature is of 13.8 °C (57 °F), with a minimum of 9.2 °C (48.5 °F) and a maximum of 18.4 °C (65.1 °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 2.7 °C (36.9 °F) in September 1993.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 25.5 °C (77.5 °F). However, it reached 35.6 °C (96.1 °F) in September 2017.
Precipitation amounts to 20 mm (0.8 in), distributed over 9 days.
The day lasts on average 12 hours and 25 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 59% of the time.
The average humidity is 87%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 14 °C (57 °F). Therefore, the sea is very cold for swimming.

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October is generally a mild month. The average temperature is of 12.4 °C (54 °F), with a minimum of 7.2 °C (45 °F) and a maximum of 17.5 °C (63.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 2 °C (35.5 °F). However, it dropped to -1.7 °C (28.9 °F) in October 2002.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 26.5 °C (79.5 °F). However, it reached 33 °C (91.4 °F) in October 2003.
Precipitation amounts to 70 mm (2.8 in), distributed over 12 days.
The day lasts on average 11 hours and 5 minutes.
There are on average 5.5 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 84%. Hence, the air is normally humid.
The average wind speed is 8 kph (5 mph).
The average sea temperature is of 13.5 °C (56 °F). Therefore, the sea is very cold for swimming.

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November is generally a mild month. The average temperature is of 10.3 °C (50 °F), with a minimum of 5.6 °C (42.1 °F) and a maximum of 14.9 °C (58.9 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 0 °C (32 °F). However, it dropped to -2.8 °C (27 °F) in November 2004.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 21 °C (70 °F). However, it reached 26.1 °C (79 °F) in November 2002.
Precipitation amounts to 145 mm (5.7 in), distributed over 17 days.
The day lasts on average 9 hours and 55 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 44% of the time.
The average humidity is 84%. Hence, the air is normally humid.
The average wind speed is 9 kph (6 mph).
The average sea temperature is of 13 °C (55 °F). Therefore, the sea is very cold for swimming.

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December, the coldest month of the year, is generally a mild month. The average temperature is of 8.9 °C (48 °F), with a minimum of 4.3 °C (39.7 °F) and a maximum of 13.4 °C (56.2 °F).
On the coldest nights of the month, the temperature usually drops to around -1.5 °C (29 °F). However, it dropped to -5.1 °C (22.8 °F) in December 1998.
On the warmest days of the month, the temperature usually reaches around 19 °C (66.5 °F). However, it reached 23.4 °C (74.1 °F) in December 1999.
Precipitation amounts to 225 mm (8.9 in), distributed over 19 days.
The day lasts on average 9 hours and 20 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 44% of the time.
The average humidity is 83%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).
The average sea temperature is of 12 °C (53.5 °F). Therefore, the sea is very cold for swimming.