The Mariners will be the home team for all three games, meaning the Padres could be in position to clinch their first playoff berth since 2006 while playing as visitors in their home ballpark.
The West Coast wildfires have caused air-quality problems in the Seattle area this week.
A two-game Giants-Mariners series scheduled for earlier this week in Seattle was postponed and moved to San Francisco, with the teams finishing it Thursday. That decision came after some players complained about smoky conditions Monday after the Mariners split a doubleheader with the Oakland Athletics.
With the move, the Mariners have three home games remaining on their schedule beginning next Monday against Houston.
Seattle manager Scott Servais said the team learned of the change around 11:15 a.m. PT, about two hours before first pitch against San Francisco. Seattle lost to the Giants 6-4.
Servais said when the team left Seattle on Wednesday morning, almost everyone believed it would be a two-day trip.
"We were led to believe that everything was going to clear up in Seattle," Servais said. "We can't control the weather. It's bigger than all of us and what's going on there with the smoke and whatnot. Certainly understand why we have to go. But I don't think anybody was really prepared for it."
According to AirNow.gov, the air-quality rating for Friday in Seattle is expected to be 149, which is deemed "unhealthy for sensitive groups." The air quality is projected to be much better Saturday and Sunday.
ESPN's Jeff Passan reported earlier this week that if the West Coast fires continue to affect Major League Baseball down the stretch, particularly with the American League Division Series and AL Championship Series scheduled to be played in California, the Phoenix area has emerged as the primary backup option if postseason games need to be moved because of air-quality problems.
Information from The Associated Press was used in this report.