Tri-Cities, WA Climate & Monthly Averages
Tri-Cities has a semi-arid climate. July is the hottest month, averaging 96° by day; January is the coldest at 42°.
Tri-Cities's climate runs on sunshine and sparse rain
Tri-Cities works on a dry budget: 10.1 inches (256 mm) of precipitation a year, spread over roughly 66 days. Temperature does the varying instead, from 42°F (5°C) on a typical January afternoon to 96°F (36°C) in July, with nights 12°C below the day.
What the dry climate changes
Overnight lows average at or below freezing for 3 months, December through February. At its warmest, in July, Tri-Cities runs to 96°F (36°C) in the afternoon and back to 67°F (20°C) by dawn. January bottoms out at 42°F (5°C) in daylight, 29°F (-2°C) after dark. July is the brightest month at 14.3 hours of sun a day, against an annual average of 9.6.
Days and nights are about 12°C apart on average - wider than roughly 88% of the cities we track. The gridded 2015-2024 daily record for this location tops out at 118°F (48°C) and bottoms at -3°F (-20°C) - decade extremes, not all-time station records.
More climate facts for Tri-Cities
- Hottest month: July - highs near 96°F (36°C)
- Coldest month: January - highs near 42°F (5°C)
- Decade extremes (2015-2024): 118°F (48°C) high · -3°F (-20°C) low
- Wettest month: December (10 rainy days) · Sunniest: July (14.3 h sun/day)
- Climate type: semi-arid
- Annual swing: 27°C between the average warmest and coolest month · day to night: 12°C
- Snow: about 7 days a year
- Months averaging 30°C or hotter: 3
- Average humidity: 55%
Heat, cold and scarce precipitation in the dataset
Derived from ERA5 reanalysis data, 2015–2024. Official station records may differ. Need another precipitation unit? Use the rainfall converter.
When the dry weather is easiest to use
Avoiding the hardest heat or cold
April to May and September to October is the sweet spot for Tri-Cities - temperatures sit either side of the peak heat rather than in it. Expect 74°F (23°C) in the afternoon and around 5 days of rain in a typical month of it. For the same question asked the other way round, see where else is warm in April.
Prepare for sun and cooler nights
Pack for Tri-Cities with lightweight, breathable clothing and serious sun protection, a warm jacket and layers for the cooler season and rain gear if you travel around December. July nights average 67°F (20°C), so evenings rarely match the afternoons.
Monthly heat and rainfall table
| Month | High | Low | Rain days | Precipitation | Sunshine | Daylight | Wet-day chance | Humidity |
|---|---|---|---|---|---|---|---|---|
| January | 42° | 29° | 10 | 1.4 in | 4.5 h/day | 9.0 h | 33% | 81% |
| February | 47° | 31° | 8 | 1.1 in | 7.0 h/day | 10.3 h | 28% | 72% |
| March | 57° | 37° | 7 | 1.0 in | 9.1 h/day | 11.8 h | 22% | 62% |
| April | 67° | 44° | 6 | 0.8 in | 11.0 h/day | 13.5 h | 18% | 46% |
| May | 79° | 54° | 4 | 0.8 in | 12.4 h/day | 15.0 h | 13% | 40% |
| June | 87° | 62° | 2 | 0.3 in | 13.7 h/day | 15.8 h | 8% | 34% |
| July | 96° | 67° | 0 | 0.0 in | 14.3 h/day | 15.4 h | 1% | 29% |
| August | 94° | 66° | 1 | 0.2 in | 13.0 h/day | 14.1 h | 3% | 34% |
| September | 82° | 57° | 2 | 0.3 in | 10.9 h/day | 12.5 h | 8% | 45% |
| October | 67° | 46° | 6 | 1.0 in | 8.6 h/day | 10.8 h | 20% | 62% |
| November | 50° | 36° | 9 | 1.5 in | 6.0 h/day | 9.3 h | 29% | 77% |
| December | 41° | 30° | 10 | 1.6 in | 4.5 h/day | 8.6 h | 33% | 81% |
How daytime heat and cool nights change by month
Each card shows the average high and low. The bar places that month between Tri-Cities's coldest night and warmest afternoon.
January
- Rain
- 10 days
- Sunshine
- 4.5 h
- Daylight
- 9.0 h
- Snow
- 2 days
February
- Rain
- 8 days
- Sunshine
- 7.0 h
- Daylight
- 10.3 h
- Snow
- 2 days
March
- Rain
- 7 days
- Sunshine
- 9.1 h
- Daylight
- 11.8 h
April
- Rain
- 6 days
- Sunshine
- 11.0 h
- Daylight
- 13.5 h
May
- Rain
- 4 days
- Sunshine
- 12.4 h
- Daylight
- 15.0 h
June
- Rain
- 2 days
- Sunshine
- 13.7 h
- Daylight
- 15.8 h
July
- Rain
- 0 days
- Sunshine
- 14.3 h
- Daylight
- 15.4 h
August
- Rain
- 1 day
- Sunshine
- 13.0 h
- Daylight
- 14.1 h
September
- Rain
- 2 days
- Sunshine
- 10.9 h
- Daylight
- 12.5 h
October
- Rain
- 6 days
- Sunshine
- 8.6 h
- Daylight
- 10.8 h
November
- Rain
- 9 days
- Sunshine
- 6.0 h
- Daylight
- 9.3 h
December
- Rain
- 10 days
- Sunshine
- 4.5 h
- Daylight
- 8.6 h
- Snow
- 2 days
Looking for warmer alternatives? Browse warm places by month, or compare Tri-Cities's coolest part of the year: December, January, February.
Heat and cold across the Tri-Cities year
Spring (March through May)
Through spring, Tri-Cities is mild: 68°F (20°C) by day, 45°F (7°C) after dark, and rain comes on about 16 days over the three months. Daylight is generous - around 10.8 hours of sun a day.
Summer (June through August)
Summer runs at full heat here - highs near 93°F (34°C), nights near 65°F (18°C), and precipitation is sparse, near 14 mm (0.5 in) for the season. Daylight is generous - around 13.7 hours of sun a day.
Fall (September through November)
Fall is crisp but comfortable here - highs near 66°F (19°C), nights near 46°F (8°C), and rain comes on about 18 days over the three months.
Winter (December through February)
Through winter, Tri-Cities is chilly: 43°F (6°C) by day, 30°F (-1°C) after dark, and expect showers on roughly 28 days across the season, plus about 6 snowy days.
How unusual is Tri-Cities?
- Annual precipitation is 10.1 inches (256 mm) - drier than all but 6% of the 3496 cities we track.
- Its warmest and coolest months are 27°C apart - a wider seasonal swing than 90% of the 3496 cities we track.
- Relative humidity averages 55% - drier than all but 10% of the 3496 cities we track.
These comparisons use the same ten-year window for every city in the dataset.