Is Tri-Cities really one of the sunniest places in Washington state? Here’s what to know

When you tell someone outside of the Evergreen State that you’re from Washington, it’s often that they think of Seattle stereotypes, like constant rain.

Many people forget, or don’t realize, that there are massive differences between eastern and western Washington, both in climate and culture. The weather on the east side has much colder winters and warmer summers, for example.

Misconceptions over these climate differences was likely a motivating factor in the push to brand Tri-Cities as having 300 sunny days per year. Over the years, the claim has been used by many local organizations as a pull to the area.

But is it really accurate? One local says no.

Why does Tri-Cities claim so much sunny weather?

So, where did the claim of 300 sunny days a year in Tri-Cities come from? It’s been attributed to different organizations over time, and used by numerous others, including local chambers of commerce, Visit Tri-Cities, the Tri-Cities Airport and the Tri-Cities Development Council. It has even been repeated by the Washington State Department of Commerce.

Numerous sources speculate that the count for Tri-Cities’ sunny days came from the work of one individual, a former president of Visit Tri-Cities. The vice president of marketing at Visit Tri-Cities, Julie Woodward, previously told the Herald she “believed” that was true, but could not offer verification either way. No one has ever officially taken credit for the claim.

Visit Tri-Cities is aimed at Northwest tourists, making the weather a major selling point. The organization often makes the claim that Tri-Cities has the “best weather in the state,” hoping to attract folks from the west side to abandon the precipitation.

“The largest percentage of our visitors come from Seattle,” Woodward stated in a prior email to the Herald. “They are looking for an escape from the rain and gray and seeking sunshine.”

Wherever the count originated, it has been deduced that the criteria for a “sunny day” was a clear sky during regular observation hours — but it didn’t have to be for a long period of time. Following this criteria, Tri-Cities may very well have an average of 300 sunny days per year.

However, a local man, Jim Zimmerlin, thought this was a misleading, counter-intuitive definition. Several years ago, after he determined that system was being used, he began recording Tri-Cities’ sunny days per year, using his own definition. Here’s what he found.

Defining a sunny Tri-Cities day

Instead of any given instance of sunshine, Zimmerlin’s methodology requires a day to have more hours of sunshine than hours of cloudiness in order to be considered a sunny day. If a majority of hours between sunrise and sunset show sunshine, that’s a sunny day. Usually six hours is the cutoff.

Using these guidelines, there were 213 sunny days in Tri-Cities in 2024, according to Zimmerlin. In 2023, there were 195 sunny days, down from the year before, which had 207 sunny days.

Zimmerlin sent the Herald a breakdown of how many sunny days were seen each month in 2023 and 2024.

In 2023, Zimmerlin’s count for sunny days was:

• January: 8

• February: 10

• March: 13

• April: 13

• May: 27

• June: 24

• July: 31

• August: 22

• September: 17

• October: 18

• November: 9

• December: 3

But in 2024, his count was:

• January: 4

• February: 8

• March: 22

• April: 19

• May: 20

• June: 22

• July: 30

• August: 28

• September: 26

• October: 20

• November: 8

• December: 6

So far for 2025, Zimmerlin has noticed a big difference from 2024. January had 17 sunny days in 2025, compared to only 4 the year prior.

He noted that people’s impression of what makes a sunny day is important to consider, that he wants to report a number most people would agree with.

He says that most days, it’s an easy call to make.

On average, there are generally only about five days a year where it’s difficult to determine one way or the other, Zimmerlin previously told the Herald. He leans toward a sunny designation on these days.

“On the vast majority of days, I think reasonable people would easily be able to agree with my determination of whether it was a sunny day or not,” Zimmerlin told the Herald in an email. “It’s an easy call to make about 360 days of the year. The other five days where the call is not so clear-cut, some people might not agree with my call… but that means my confidence factor in the reliability of my numbers is 360 out of 365, or 92%.”