January is one of the cooler months of the year in Boise, with average highs near 2.4°C and lows around -5.3°C (mean -1.4°C). It is a relatively wet time of year, averaging 51 mm of rainfall and 82% relative humidity across the period.
January is one of the cooler months of the year in Boise. Across 45 years of records, the warmest January in Boise was 2003 — when the month averaged 3°C — while the coldest was 2017 at -7.1°C. Typical January days reach 2.4°C with nights near -5.3°C. The long-term trend is warming, about 0.3°C per decade.
January is a relatively wet time of year in Boise, averaging 51 mm of rainfall. The wettest January on record was 2017 with 118 mm, while the driest was 1985 at 5 mm.
Relative humidity in Boise during January averages 82%. The most humid January was 1984 at 92%, and the least humid was 2012 at 72%.
January receives about 1.7 kWh/m²/day of solar energy in Boise. The sunniest January was 2007 at 2.2 kWh/m²/day, and the cloudiest were 1990 and 2004 at 1.4.
Average wind speed in Boise during January is 2.1 m/s. The windiest January was 2008 at 2.9 m/s, while the calmest was 1985 at 1.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | -2.7°C | -1.0°C | -1.2°C | -1.3°C | -1.0°C | +1.7°C |
| Avg High | 1.3°C | 2.9°C | 2.7°C | 2.5°C | 2.9°C | +1.6°C |
| Avg Low | -6.7°C | -4.9°C | -5.1°C | -5.2°C | -4.8°C | +1.9°C |
| Avg Rain | 37 mm | 59 mm | 43 mm | 57 mm | 62 mm | +25 mm |
January temperatures in Boise have risen by about 1.5°C between 1981–1985 and 2021–2025.
January has ranged from a record low of -22.7°C (2017) to a record high of 14.7°C (2024).
Rainfall in January is a relatively wet time of year, averaging 51 mm, with a wettest year of 118 mm.
A quieter season to visit Boise
If your dates are flexible, the more temperate months of August and July tend to be the most comfortable for visiting Boise. That said, January — with days averaging 2.4°C and nights around -5.3°C (mean -1.4°C) and moderate rainfall (51 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 | 3.1°C | -0.9°C | -4.8°C | 6.8°C | -9.8°C | 41 mm | 76% | 1.7 m/s | 2.1 |
| 2024 | 2.3°C | -1.4°C | -5.1°C | 14.7°C | -20.9°C | 99 mm | 87% | 2.4 m/s | 1.6 |
| 2023 | 2.9°C | -1.0°C | -4.8°C | 7.4°C | -13.7°C | 39 mm | 82% | 2.5 m/s | 1.7 |
| 2022 | 0.3°C | -3.7°C | -7.6°C | 3.5°C | -19.5°C | 51 mm | 87% | 1.7 m/s | 1.8 |
| 2021 | 4.0°C | 0.3°C | -3.4°C | 7.7°C | -7.1°C | 58 mm | 78% | 2.3 m/s | 1.8 |
| 2020 | 4.7°C | 0.7°C | -3.3°C | 10.6°C | -12.4°C | 82 mm | 80% | 2.3 m/s | 1.5 |
| 2019 | 4.1°C | 0.1°C | -4.0°C | 8.3°C | -13.2°C | 51 mm | 78% | 2.3 m/s | 1.9 |
| 2018 | 5.6°C | 2.0°C | -1.7°C | 12.6°C | -6.0°C | 63 mm | 78% | 2.1 m/s | 1.7 |
| 2017 ❄️ 🌧️ | -2.7°C | -7.1°C | -11.5°C | 2.4°C | -22.7°C | 118 mm | 91% | 1.9 m/s | 1.5 |
| 2016 | 1.9°C | -1.7°C | -5.4°C | 7.3°C | -17.0°C | 58 mm | 86% | 2.2 m/s | 1.7 |
| 2015 | 3.5°C | 0.1°C | -3.4°C | 9.3°C | -14.3°C | 35 mm | 85% | 1.4 m/s | 1.7 |
| 2014 | 3.5°C | -0.2°C | -3.9°C | 7.9°C | -8.9°C | 32 mm | 74% | 1.7 m/s | 1.8 |
| 2013 | -1.0°C | -5.0°C | -9.0°C | 7.2°C | -17.1°C | 29 mm | 87% | 1.9 m/s | 1.9 |
| 2012 | 4.1°C | 0.0°C | -4.1°C | 10.9°C | -11.2°C | 83 mm | 72% | 2.2 m/s | 1.8 |
| 2011 | 1.9°C | -1.9°C | -5.6°C | 8.5°C | -17.6°C | 39 mm | 84% | 1.6 m/s | 1.8 |
| 2010 | 3.8°C | 0.2°C | -3.3°C | 8.7°C | -12.3°C | 67 mm | 82% | 2.6 m/s | 1.6 |
| 2009 | 2.4°C | -1.7°C | -5.8°C | 7.6°C | -15.0°C | 33 mm | 81% | 1.7 m/s | 1.6 |
| 2008 | 0.6°C | -3.6°C | -7.7°C | 6.8°C | -15.1°C | 48 mm | 81% | 2.9 m/s | 1.7 |
| 2007 | 1.5°C | -2.8°C | -7.0°C | 7.4°C | -15.6°C | 14 mm | 77% | 1.9 m/s | 2.2 |
| 2006 | 3.9°C | 0.5°C | -2.9°C | 9.3°C | -6.2°C | 78 mm | 82% | 2.6 m/s | 1.5 |
| 2005 | 4.4°C | 0.2°C | -3.9°C | 10.3°C | -10.4°C | 15 mm | 81% | 2 m/s | 1.7 |
| 2004 | 0.4°C | -3.4°C | -7.3°C | 4.2°C | -20.1°C | 58 mm | 88% | 2.1 m/s | 1.4 |
| 2003 🔥 | 6.8°C | 3.0°C | -0.9°C | 13.9°C | -5.2°C | 53 mm | 82% | 1.6 m/s | 1.5 |
| 2002 | 2.0°C | -1.5°C | -5.0°C | 6.4°C | -11.6°C | 38 mm | 81% | 2.3 m/s | 1.6 |
| 2001 | 2.1°C | -2.1°C | -6.3°C | 6.5°C | -10.9°C | 29 mm | 78% | 1.8 m/s | 1.6 |
| 2000 | 3.2°C | -0.3°C | -3.8°C | 8.4°C | -9.3°C | 66 mm | 82% | 2.1 m/s | 1.5 |
| 1999 | 3.6°C | -0.1°C | -3.8°C | 9.2°C | -11.2°C | 54 mm | 77% | 2.2 m/s | 1.6 |
| 1998 | 3.9°C | 0.1°C | -3.6°C | 9.6°C | -10.0°C | 96 mm | 83% | 2.3 m/s | 1.5 |
| 1997 | 2.0°C | -1.7°C | -5.4°C | 7.9°C | -17.3°C | 97 mm | 84% | 2.1 m/s | 1.7 |
| 1996 | 2.5°C | -1.3°C | -5.0°C | 8.4°C | -18.2°C | 70 mm | 83% | 2.3 m/s | 1.5 |
| 1995 | 4.0°C | 0.4°C | -3.3°C | 10.5°C | -12.9°C | 75 mm | 81% | 2.6 m/s | 1.7 |
| 1994 | 4.5°C | 0.8°C | -3.0°C | 9.7°C | -7.8°C | 43 mm | 78% | 1.8 m/s | 1.7 |
| 1993 | -0.8°C | -5.4°C | -10.0°C | 2.6°C | -16.2°C | 60 mm | 89% | 2.1 m/s | 1.8 |
| 1992 | 3.6°C | -0.2°C | -4.1°C | 11.7°C | -8.6°C | 15 mm | 76% | 2.3 m/s | 1.7 |
| 1991 | 1.6°C | -2.7°C | -7.1°C | 6.8°C | -13.3°C | 39 mm | 77% | 1.9 m/s | 1.8 |
| 1990 | 3.7°C | 0.2°C | -3.3°C | 10.2°C | -8.6°C | 47 mm | 77% | 2.3 m/s | 1.4 |
| 1989 | -0.6°C | -4.7°C | -8.9°C | 3.7°C | -14.2°C | 49 mm | 90% | 1.9 m/s | 1.7 |
| 1988 | 0.7°C | -3.2°C | -7.2°C | 5.9°C | -15.1°C | 52 mm | 82% | 2 m/s | 1.7 |
| 1987 | 1.5°C | -2.8°C | -7.1°C | 11.2°C | -17.7°C | 37 mm | 81% | 2 m/s | 1.7 |
| 1986 | 4.3°C | 0.5°C | -3.3°C | 10.3°C | -10.4°C | 41 mm | 82% | 2.6 m/s | 1.6 |
| 1985 | -0.7°C | -4.9°C | -9.1°C | 3.9°C | -15.0°C | 5 mm | 86% | 1.2 m/s | 1.9 |
| 1984 | -1.2°C | -5.1°C | -9.1°C | 3.9°C | -21.1°C | 20 mm | 92% | 1.5 m/s | 1.7 |
| 1983 | 3.8°C | 0.3°C | -3.1°C | 7.9°C | -13.0°C | 52 mm | 84% | 2.3 m/s | — |
| 1982 | -1.4°C | -5.5°C | -9.5°C | 3.8°C | -21.7°C | 50 mm | 90% | 2.2 m/s | — |
| 1981 | 5.5°C | 1.3°C | -2.9°C | 11.5°C | -7.6°C | 28 mm | 75% | 2.2 m/s | — |
Actual recorded January data for each year, 1981–2025 — sourced from NASA POWER.
The average high in January is around 2.4°C with lows near -5.3°C (mean -1.4°C), based on 45 years of NASA POWER data.
January averages 51 mm of rainfall in Boise, a relatively wet time of year. The wettest on record was 118 mm in 2017.
The hottest January reached 14.7°C in 2024. The coldest dipped to -22.7°C in 2017.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average January temperatures have risen by about 1.5°C. Daytime highs moved from 1.2°C to 2.5°C and overnight lows from -6.7°C to -5.1°C over the same span.
January is one of the cooler months of the year in Boise and a relatively wet time of year, so plan for around 2.4°C daytime highs and -5.3°C at night.
Yes — January is the coldest month of the year in Boise, averaging -1.4°C.
For January in Boise, pack warm layers and a jacket for chilly mornings, with typical highs of 2.4°C and lows of -5.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in January averages 82% — quite humid.
Average wind speed in January is 2.1 m/s. The windiest January on record averaged 2.9 m/s (2008).
The wettest January on record was 2017 with 118 mm. On average, January sees 51 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 Boise 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.
