Tri-Cities climate
Tri-Cities (Washington, United States) has a cold semi-arid climate (Köppen BSk). The average temperature over the year is 14 °C57 °F, and about 278 mm11 in of precipitation falls in an average year.
Temperature by month
Precipitation by month
Tri-Cities climate table
| Month | High °C°F | Low °C°F | Mean °C°F | Precip. mmin |
|---|---|---|---|---|
| Jan | 644 | −130 | 337 | 361.4 |
| Feb | 1049 | 032 | 541 | 251.0 |
| Mar | 1558 | 338 | 948 | 271.1 |
| Apr | 1966 | 643 | 1254 | 241.0 |
| May | 2576 | 1152 | 1864 | 271.0 |
| Jun | 2984 | 1558 | 2271 | 210.8 |
| Jul | 3594 | 1865 | 2680 | 40.2 |
| Aug | 3392 | 1864 | 2678 | 70.3 |
| Sep | 2781 | 1356 | 2068 | 110.4 |
| Oct | 1966 | 846 | 1356 | 240.9 |
| Nov | 1152 | 236 | 744 | 291.2 |
| Dec | 643 | −130 | 337 | 421.7 |
| Year | 3594 | −130 | 1457 | 27811 |
“Year” row: highest monthly high, lowest monthly low, annual mean and annual total.
| Month | Humid. | Cloud | Solar | Daylight |
|---|---|---|---|---|
| Jan | 81% | 79% | 1.2 | 8:59 |
| Feb | 72% | 68% | 2.3 | 10:16 |
| Mar | 64% | 69% | 3.6 | 11:46 |
| Apr | 58% | 61% | 5.4 | 13:30 |
| May | 52% | 56% | 6.5 | 14:57 |
| Jun | 48% | 46% | 7.2 | 15:46 |
| Jul | 41% | 26% | 7.7 | 15:26 |
| Aug | 41% | 29% | 6.4 | 14:09 |
| Sep | 47% | 39% | 4.7 | 12:28 |
| Oct | 60% | 56% | 3.0 | 10:49 |
| Nov | 71% | 70% | 1.6 | 9:21 |
| Dec | 79% | 77% | 1.0 | 8:38 |
Humid. = average relative humidity at 2 m; cloud = average cloud amount; solar = average daily solar energy reaching the ground in kWh/m² (all-sky); daylight in hours:minutes, calculated for the 15th of each month.
What the climate of Tri-Cities is like
The warmest month is July, with an average high of 35 °C94 °F and a low of 18 °C65 °F. The coldest is December, when highs average 6 °C43 °F and lows −1 °C30 °F. Seasons are strongly marked: the warmest month is on average 23.8 °C42.9 °F warmer than the coldest.
It is dry, with about 278 mm11 in of precipitation per year. The wettest three-month stretch is November–January, which brings 39% of the annual total. Months with less than 20 mm0.8 in on average: July–September. The wettest month is December (42 mm1.7 in), the driest is July (4 mm0.2 in).
Relative humidity ranges from 41% in August to 81% in January. The clearest skies (lowest average cloud amount, 26%) are typical of July. Average wind speed near the ground ranges from 8 km/h (5 mph) in September to 10 km/h (6 mph) in June. Daylight lasts from about 8.6 hours in December to 15.8 hours in June.
A lasting snow cover is typical in December and January, when the average snow depth in the reanalysis exceeds 10 cm (deepest in January, about 13 cm).
Best time to visit Tri-Cities
Based on these averages, the most comfortable months for sightseeing and outdoor activities are April–June and September and October: average highs of 19 °C66 °F to 29 °C84 °F with 11 mm0.4 in to 27 mm1.0 in of precipitation per month.
The most challenging month is December, which is cold, with average highs of 6 °C43 °F.
Comfort score: months are ranked by how close they come to an average high of 21–28 °C (70–82 °F), lows above 5 °C (41 °F), little precipitation and moderate humidity. The best-ranked months of each place are recommended, even where none meets all of these. These are general rules of thumb applied to long-term averages.
What to pack for Tri-Cities
- Winter (December–February) — highs 643 to 10 °C49 °F, lows −130 to 0 °C32 °F, about 35 mm1.4 in of precipitation a month. Pack a warm coat, layers and closed shoes and shoes with good grip, as frost is common.
- Spring (March–May) — highs 1558 to 25 °C76 °F, lows 338 to 11 °C52 °F, about 26 mm1.0 in of precipitation a month. Pack light layers — T-shirts plus a light sweater or jacket and an extra layer for the cooler mornings and evenings.
- Summer (June–August) — highs 2984 to 35 °C94 °F, lows 1558 to 18 °C65 °F, about 11 mm0.4 in of precipitation a month. Pack very light, breathable clothing, a sun hat and plenty of water and an extra layer for the cooler mornings and evenings.
- Autumn (September–November) — highs 1152 to 27 °C81 °F, lows 236 to 13 °C56 °F, about 21 mm0.8 in of precipitation a month. Pack light layers — T-shirts plus a light sweater or jacket and an extra layer for the cooler mornings and evenings.
How Tri-Cities compares
Compared with Portland, about 281 km to the west, Tri-Cities is on average 1.6 °C2.9 °F warmer and receives 81% less precipitation (278 mm11 in vs 1,484 mm58 in). The difference is largest in July (6 °C10.8 °F warmer).
Of the 222 places in the United States covered by World Climates, Tri-Cities is the 124th warmest by annual mean temperature and the 210th wettest by annual precipitation. See all of them on the United States climate page.
Places in other countries with the most similar temperature and rainfall pattern: Aksaray (Turkey, BSk), Ereğli (Turkey, Csa) and Parla (Spain, BSk).
Nearby places
- Spokane 207 km · 9 °C49 °F · 552 mm22 in
- Portland 281 km · 12 °C54 °F · 1,484 mm58 in
- Seattle 282 km · 11 °C52 °F · 1,232 mm49 in
- Everett 298 km · 11 °C52 °F · 1,253 mm49 in
- Hillsboro 304 km · 11 °C52 °F · 1,495 mm59 in
- Salem 332 km · 11 °C53 °F · 1,370 mm54 in
- Boise 376 km · 12 °C54 °F · 389 mm15 in
- Chilliwack 385 km · 11 °C51 °F · 1,815 mm71 in
Frequently asked questions
What is the warmest month in Tri-Cities?
July is the warmest month in Tri-Cities, with an average high of 35 °C (94 °F) and an average low of 18 °C (65 °F).
What is the coldest month in Tri-Cities?
December is the coldest month, with an average high of 6 °C (43 °F) and an average low of -1 °C (30 °F).
When does it rain the most in Tri-Cities?
December is the wettest month with about 42 mm (1.7 in) of precipitation; July is the driest with about 4 mm (0.2 in).
What is the best time to visit Tri-Cities?
Judging by long-term averages, the most comfortable months are April–June and September and October.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 312 m, while Tri-Cities lies at about 106 m. Temperatures on this page were therefore adjusted by +1.3 °C2.4 °F using the standard lapse rate of 6.5 °C per 1,000 m.