Foster City's Summer Days festival, running August 14–16 at Leo J. Ryan Park, is replacing its traditional rubber duck races with a weekend-long scavenger hunt for 54 hidden rubber ducks — the change forced by construction — with prizes and a grand-prize raffle for finders.

At Leo J. Ryan Park — 670 Shell Boulevard in Foster City — the rubber duck races aren't happening this year. Construction rearranged the park enough that the traditional format didn't fit, so the city is trying something new: a scavenger hunt, with 54 rubber ducks hidden across the festival grounds, waiting for whoever finds them first.

Summer Days, the city's fourth annual outdoor celebration (it debuted in 2019), runs August 14 through 16. Admission is free; carnival rides require tickets, sold at a discount online through August 13 and only on-site after that.

On Saturday, August 15, finders have a full day — 10 a.m. to 5 p.m. — to bring a duck to the Information Booth near The Vibe Teen Center for a small prize and a raffle entry. On Sunday, August 16, that window closes at 11:30 a.m. The grand prize winner is announced on social media at 12:30 p.m. Sunday; posting a photo and tagging @fcrecreation with a found duck earns a second entry, per the festival's official rules.

Shell Boulevard between East Hillsdale Boulevard and Foster Square Lane closes to through traffic starting August 11; the segment from Foster Square Lane to Bounty Drive, along with Balclutha Drive, closes August 13. Event parking runs $10 at Parkside Towers (1031 E. Hillsdale Blvd.) and Century Lot (1065 E. Hillsdale Blvd.); Sports Basement provides complimentary bike valet on Saturday and Sunday from 11 a.m. to 5 p.m.

Friday's opener runs in the evening: a classic car show on Shell Boulevard from 4 to 7 p.m., then Mercy & the Heartbeats in the amphitheater from 6 to 8 p.m., with food service from 5 p.m. Saturday runs longest — carnival rides until 11 p.m., food vendors through 8 p.m., craft and community booths through the afternoon. San Jose Made returns with more than 100 artists from across the Bay Area. Sunday wraps earlier: rides until 7 p.m., most everything else by 5.

By 12:30 Sunday afternoon, 54 small rubber birds will have either been claimed or are still out there somewhere — tucked under a bench, behind a food cart, waiting for one last pass through the grounds.