Weather in Tri-Cities in August

A good month. August is a solid month to be in Tri-Cities. Highs average 33.2 °C, lows 18.1 °C, and rain falls on 2 days — nothing in the month is working against you.

August ranks 7 of 12 in Tri-Cities: past the worst of the year but short of September, which is the month to book if the dates are open.

Rain falls on only 2 days, so an itinerary with no wet-weather fallback is a reasonable risk. Pack for 33.2 °C days and 18.1 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 10 days clear 35 °C, so a serious heatwave is normal rather than notable; the day swings 15.1 °C from low to high, which means one bag has to cover both. Across the twenty years measured, the hottest August day reached 43.7 °C and the coldest night fell to 10.4 °C.

August is dependably dry, and that reliability is the point: across the twenty years measured, the wettest August on record still only managed 24 mm, and the driest managed 1 mm. There is no meaningful variability to plan around, which makes this one of the few months anywhere that you can build a fixed outdoor itinerary against without a fallback. The wettest single day in twenty years of Augusts brought 11 mm. Rain simply is not the variable that decides this trip — heat, crowds and cost are.

Wind is light at 8.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 41%.

How August sits in the year

Temperatures hold steady either side: 34.3 °C in July, 33.2 here, 27.4 in September. Nothing about the timing within the month matters much.

Daylight in August

14.2 hours of daylight, losing 1.4 hours across the month. That is between Tri-Cities's extremes of 15.8 and 8.6 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 34.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage. Within August itself the daily swing is 15.1 °C, so mornings and afternoons need different clothes.

How busy it gets

Busy. Popular without being frantic; book the things you care about, improvise the rest.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

August in Tri-Cities versus nearby

If Tri-Cities is one option among several, the nearby comparison is worth making. Spokane is a better bet in August — 3.9 °C cooler, 1 day more rain. Portland is a better bet in August — 3.3 °C cooler, 1 day more rain.

So: August is a compromise. September is 24 points better and is what Tri-Cities is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Tri-Cities

See all twelve months in Tri-Cities, or where else to go in August.