January is one of the cooler months of the year in Issaquah, with average highs near 4.2°C and lows around -1°C (mean 1.6°C). It is a relatively wet time of year, averaging 245 mm of rainfall and 92% relative humidity across the period.
January is one of the cooler months of the year in Issaquah. Across 45 years of records, the warmest January in Issaquah was 2015 — when the month averaged 4.8°C — while the coldest was 1993 at -2.1°C. Typical January days reach 4.2°C with nights near -1°C. The long-term January temperature trend is broadly flat.
January is a relatively wet time of year in Issaquah, averaging 245 mm of rainfall. The wettest January on record was 2006 with 453 mm, while the driest was 1985 at 28 mm.
Relative humidity in Issaquah during January averages 92%. The most humid January was 2006 at 97%, and the least humid was 1981 at 86%.
January receives about 1.1 kWh/m²/day of solar energy in Issaquah. The sunniest January was 2025 at 1.4 kWh/m²/day, and the cloudiest was 1999 at 0.7.
Average wind speed in Issaquah during January is 0.3 m/s. The windiest January was 2022 at 0.4 m/s, while the calmest was 2016 at 0.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 1.4°C | 1.4°C | 1.6°C | 2.1°C | 1.8°C | +0.4°C |
| Avg High | 4.1°C | 4.0°C | 4.1°C | 4.7°C | 4.3°C | +0.2°C |
| Avg Low | -1.3°C | -1.3°C | -0.9°C | -0.6°C | -0.6°C | +0.7°C |
| Avg Rain | 237 mm | 260 mm | 264 mm | 216 mm | 251 mm | +14 mm |
January temperatures in Issaquah have stayed relatively stable across the record.
January has ranged from a record low of -20.3°C (1996) to a record high of 18.4°C (2015).
Rainfall in January is a relatively wet time of year, averaging 245 mm, with a wettest year of 453 mm.
A quieter season to visit Issaquah
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Issaquah. That said, January — with days averaging 4.2°C and nights around -1°C (mean 1.6°C) and higher rainfall (245 mm) — can still be rewarding for travellers who don't mind the cooler conditions, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 3.7°C | 0.7°C | -2.4°C | 6.8°C | -7.8°C | 93 mm | 89% | 0.3 m/s | 1.4 |
| 2024 | 3.0°C | 0.6°C | -1.7°C | 13.7°C | -18.1°C | 291 mm | 94% | 0.3 m/s | 1 |
| 2023 | 4.6°C | 2.3°C | -0.1°C | 8.8°C | -8.0°C | 123 mm | 90% | 0.3 m/s | 1.1 |
| 2022 | 5.0°C | 2.2°C | -0.5°C | 8.6°C | -15.7°C | 308 mm | 90% | 0.4 m/s | 1.1 |
| 2021 | 5.3°C | 2.9°C | 0.4°C | 9.9°C | -4.7°C | 252 mm | 91% | 0.3 m/s | 1.1 |
| 2020 | 4.3°C | 2.3°C | 0.4°C | 9.7°C | -6.8°C | 440 mm | 97% | 0.3 m/s | 0.8 |
| 2019 | 6.1°C | 3.2°C | 0.4°C | 9.8°C | -3.0°C | 144 mm | 87% | 0.3 m/s | 1.2 |
| 2018 | 5.0°C | 3.1°C | 1.2°C | 9.1°C | -3.0°C | 284 mm | 94% | 0.3 m/s | 0.9 |
| 2017 | 1.4°C | -1.9°C | -5.1°C | 7.0°C | -12.7°C | 93 mm | 91% | 0.3 m/s | 1.3 |
| 2016 | 4.2°C | 1.7°C | -0.7°C | 10.0°C | -7.7°C | 222 mm | 95% | 0.2 m/s | 1.1 |
| 2015 🔥 | 8.2°C | 4.8°C | 1.5°C | 18.4°C | -6.1°C | 208 mm | 89% | 0.3 m/s | 1.2 |
| 2014 | 6.2°C | 3.2°C | 0.1°C | 12.6°C | -3.2°C | 214 mm | 88% | 0.3 m/s | 1.1 |
| 2013 | 2.8°C | 0.5°C | -1.8°C | 6.7°C | -6.9°C | 199 mm | 89% | 0.3 m/s | 1.1 |
| 2012 | 3.0°C | 0.8°C | -1.4°C | 8.8°C | -6.6°C | 275 mm | 92% | 0.3 m/s | 0.9 |
| 2011 | 4.0°C | 1.5°C | -1.1°C | 13.3°C | -10.6°C | 326 mm | 93% | 0.3 m/s | 1 |
| 2010 | 6.2°C | 3.8°C | 1.3°C | 9.5°C | -3.7°C | 200 mm | 90% | 0.3 m/s | 0.9 |
| 2009 | 2.8°C | 0.2°C | -2.4°C | 5.6°C | -8.2°C | 326 mm | 91% | 0.3 m/s | 1.2 |
| 2008 | 1.6°C | -0.7°C | -3.0°C | 5.8°C | -10.3°C | 209 mm | 93% | 0.3 m/s | 1.1 |
| 2007 | 3.4°C | 0.4°C | -2.6°C | 9.1°C | -11.0°C | 235 mm | 91% | 0.3 m/s | 1.2 |
| 2006 🌧️ | 4.7°C | 3.0°C | 1.4°C | 9.1°C | -1.2°C | 453 mm | 97% | 0.3 m/s | 0.8 |
| 2005 | 6.1°C | 2.8°C | -0.4°C | 16.2°C | -10.2°C | 187 mm | 90% | 0.3 m/s | 1.1 |
| 2004 | 3.6°C | 1.2°C | -1.3°C | 9.7°C | -16.8°C | 314 mm | 95% | 0.3 m/s | 0.9 |
| 2003 | 7.4°C | 4.4°C | 1.5°C | 12.3°C | -2.7°C | 297 mm | 89% | 0.3 m/s | 1.1 |
| 2002 | 3.4°C | 1.4°C | -0.5°C | 10.4°C | -6.4°C | 302 mm | 95% | 0.3 m/s | 0.9 |
| 2001 | 4.9°C | 2.2°C | -0.4°C | 9.1°C | -5.1°C | 116 mm | 89% | 0.3 m/s | 1.1 |
| 2000 | 3.0°C | 0.6°C | -1.7°C | 5.3°C | -4.3°C | 199 mm | 94% | 0.3 m/s | 1.1 |
| 1999 | 4.1°C | 2.1°C | 0.0°C | 7.3°C | -5.7°C | 255 mm | 94% | 0.3 m/s | 0.7 |
| 1998 | 3.7°C | 1.3°C | -1.1°C | 10.8°C | -14.3°C | 289 mm | 94% | 0.3 m/s | 1.1 |
| 1997 | 3.4°C | 0.7°C | -2.0°C | 10.0°C | -11.7°C | 296 mm | 91% | 0.3 m/s | 1.2 |
| 1996 | 2.4°C | -0.1°C | -2.7°C | 9.3°C | -20.3°C | 317 mm | 96% | 0.3 m/s | 1.1 |
| 1995 | 5.1°C | 2.4°C | -0.4°C | 11.0°C | -7.1°C | 212 mm | 87% | 0.3 m/s | 1.2 |
| 1994 | 6.8°C | 4.2°C | 1.6°C | 13.3°C | -2.5°C | 160 mm | 92% | 0.3 m/s | 1.2 |
| 1993 ❄️ | 1.4°C | -2.1°C | -5.6°C | 10.7°C | -14.6°C | 158 mm | 93% | 0.3 m/s | 1.3 |
| 1992 | 5.5°C | 2.9°C | 0.3°C | 10.6°C | -6.3°C | 276 mm | 91% | 0.3 m/s | 1 |
| 1991 | 3.2°C | 0.4°C | -2.4°C | 8.7°C | -12.1°C | 220 mm | 88% | 0.3 m/s | 1.2 |
| 1990 | 4.0°C | 1.7°C | -0.5°C | 7.9°C | -4.6°C | 416 mm | 95% | 0.3 m/s | 1.1 |
| 1989 | 2.9°C | 0.8°C | -1.4°C | 7.2°C | -5.8°C | 289 mm | 95% | 0.3 m/s | 1.1 |
| 1988 | 3.0°C | 0.3°C | -2.4°C | 9.3°C | -10.0°C | 175 mm | 90% | 0.3 m/s | 1.1 |
| 1987 | 3.2°C | 0.3°C | -2.6°C | 11.3°C | -12.6°C | 236 mm | 92% | 0.3 m/s | 1.1 |
| 1986 | 5.8°C | 3.3°C | 0.9°C | 10.3°C | -2.3°C | 280 mm | 91% | 0.3 m/s | 0.9 |
| 1985 | 3.3°C | -0.2°C | -3.6°C | 9.4°C | -6.8°C | 28 mm | 89% | 0.3 m/s | 1.2 |
| 1984 | 5.0°C | 2.2°C | -0.7°C | 11.1°C | -8.6°C | 323 mm | 91% | 0.3 m/s | 1.1 |
| 1983 | 5.4°C | 2.9°C | 0.3°C | 11.0°C | -6.1°C | 351 mm | 92% | 0.3 m/s | — |
| 1982 | 1.0°C | -0.9°C | -2.9°C | 4.6°C | -16.2°C | 376 mm | 96% | 0.3 m/s | — |
| 1981 | 7.5°C | 4.2°C | 0.9°C | 11.1°C | -2.4°C | 76 mm | 86% | 0.3 m/s | — |
Actual recorded January data for each year, 1981–2025 — sourced from NASA POWER.
The average high in January is around 4.2°C with lows near -1°C (mean 1.6°C), based on 45 years of NASA POWER data.
January averages 245 mm of rainfall in Issaquah, a relatively wet time of year. The wettest on record was 453 mm in 2006.
The hottest January reached 18.4°C in 2015. The coldest dipped to -20.3°C in 1996.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average January temperatures have risen by about 0.1°C — but days and nights have moved in opposite directions. Overnight lows rose from -1.2°C to -0.9°C while daytime highs eased from 4.4°C to 4.3°C, narrowing the gap between day and night.
January is one of the cooler months of the year in Issaquah and a relatively wet time of year, so plan for around 4.2°C daytime highs and -1°C at night.
Not quite — January is the 2nd coolest month in Issaquah, averaging 1.6°C.
For January in Issaquah, pack warm layers and a jacket for chilly mornings, with typical highs of 4.2°C and lows of -1°C. Bring an umbrella or light rain jacket too.
Relative humidity in January averages 92% — quite humid.
Average wind speed in January is 0.3 m/s. The windiest January on record averaged 0.4 m/s (2022).
The wettest January on record was 2006 with 453 mm. On average, January sees 245 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Issaquah behaves each January, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for January specifically, along with year-by-year records and how the month has changed over the decades.
