January Weather in Issaquah, United States

Last updated: June 24, 2025

In January, the average temperature in Issaquah, United States hovers around 5°C (40°F). Expect a chilly minimum of -12°C (11°F) and a mild maximum reaching 15°C (59°F). With an average precipitation of 199 mm (7.9 in) spread over 16 days, be prepared for some wet weather. Don’t forget your umbrella, as the average humidity sits at a damp 86%!

January Temperature in Issaquah

In January in Issaquah, the average temperature is 5°C (40°F). The maximum can reach 15°C (59°F) and the minimum can be as low as -12°C (11°F). Pack accordingly for a mix of chilly and mild weather during your travels.

January Weather in Issaquah: Daily Temperature Highs, Lows, and Averages

The chart illustrates January temperature patterns in Issaquah, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Issaquah, January typically has an average temperature of 5°C (40°F), with highs reaching up to 15°C (59°F) and lows dropping to around -12°C (11°F).

Data source: Temperature data for Issaquah generated using information from the Copernicus Climate Change Service.

January Precipitation in Issaquah

In Issaquah in January, the total precipitation amount is 199 mm (7.9 in) spread over 16 days.

January Precipitation Trends in Issaquah

The chart displays monthly precipitation patterns in Issaquah, with values for each month alongside January’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how January’s conditions compare to those of other months. In Issaquah, January typically receives around 199 mm (7.9 inches) of precipitation spread over approximately 16 days.

Data source: Precipitation data for January generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

January Humidity in Issaquah

In Issaquah in January humidity is 86%. With an average temperature of 5°C (40°F), this humidity feels like wrapping yourself in a damp blanket—uncomfortably heavy and chilly, making it difficult to enjoy outdoor activities without the constant chill seeping in.

January Average Humidity in Issaquah

This chart illustrates the average monthly humidity levels in Issaquah, with January’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In January, average humidity in Issaquah is approximately 86%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for January generated using information from the Copernicus Climate Change Service.

January UV Index in Issaquah

In Issaquah in January, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Issaquah, you can visit Hourly UV Index in Issaquah.

Maximum UV Index Levels in Issaquah for January

The chart shows the monthly maximum UV Index (UVI) for Issaquah in January, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In January, the maximum UV index in Issaquah typically reaches 2, which falls under the low exposure category.

Data source: Issaquah January UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How January Weather in Issaquah Compares to Other Months

Weather in Issaquah varies notably across the year, with each month offering distinct climate conditions. This page compares January’s weather to other months in Issaquah, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Issaquah, showing how January’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	5°C (40°F)	199 mm (7.9 inches)	86%	low
February Weather	4°C (39°F)	234 mm (9.2 inches)	86%	moderate
March Weather	7°C (44°F)	152 mm (6.0 inches)	87%	moderate
April Weather	9°C (49°F)	144 mm (5.7 inches)	84%	high
May Weather	13°C (55°F)	85 mm (3.3 inches)	81%	very high
June Weather	16°C (60°F)	78 mm (3.1 inches)	82%	very high
July Weather	18°C (65°F)	28 mm (1.1 inches)	79%	very high
August Weather	18°C (65°F)	23 mm (0.9 inches)	63%	very high
September Weather	15°C (60°F)	115 mm (4.5 inches)	62%	high
October Weather	10°C (50°F)	204 mm (8.1 inches)	83%	moderate
November Weather	7°C (45°F)	217 mm (8.5 inches)	89%	low
December Weather	4°C (40°F)	235 mm (9.3 inches)	88%	low