Cities that grow during the daytime

An influx of workers makes some cities double in size every day

While most places shrink as their workers head out to jobs elsewhere, some cities in the central Puget Sound region get bigger. A lot bigger.

We calculated the number of in-coming workers versus the number of out-going workers to find each city’s daytime population. Would you believe the spot with the largest percentage increase is…Tukwila?

The City of Opportunity expands 130% every weekday, adding the equivalent of a second Tukwila and then some. Even Redmond, home to Microsoft’s huge campus, can’t beat Tukwila’s percentage growth during the 9 to 5 hours.

Among the top employers Tukwila reports are Boeing, King County Metro and businesses in Westfield Southcenter Mall.

Fife is the runner-up city, growing by 109% daily (with many in-commuters likely headed to jobs at the Emerald Queen Hotel and Casino).

Redmond ranks third, with a weekday surge of 105%.

How about the place with the highest numeric change? No surprise: Seattle blows everybody else out of the water. The Emerald City swells by 176,000 each day—that’s the equivalent of bringing over every resident of Bellevue and Issaquah.

When its daytime population rises to 864,000, Seattle has more people than live in the City of San Francisco.

To calculate these numbers, we used American Community Survey 2013-2017 data, which are based on an average across the five-year period. View all cities that grew during the day.

Daytime population data helps cities plan infrastructure for workers and prepare for emergency evacuations.