Saturday, August 15 is the most overbooked day Long Island has had all summer. There is a street fair with two pierogi eating contests a day in Riverhead, a free five-band festival on a farm ten minutes up the road, an oyster celebration on the Port Jefferson waterfront, bluegrass on the water in Copiague, a free harbor day in Oyster Bay, and the final night of a feast that has been running in Westbury since 1910. Friday has a party and a ribbon cutting of its own. Here is how to work it, with the times that matter and one honest sentence on why each is worth the drive.

Friday: a supermarket ribbon cutting that is actually a big deal, then a late night in Patchogue

Uncle Giuseppe's Marketplace opens its new store at 130 Wheatley Plaza in Greenvale on Friday, with a ribbon cutting set for 11 a.m. A grocery opening does not usually make a weekend list, but this one fills the dark former Stop & Shop box that has been dragging on the plaza, and the company says roughly 250 people will work there. If you have ever driven the Glen Cove Road and Northern Boulevard junction and watched that empty anchor space, Friday is the day it comes back on. Expect the parking lot to be a scene, and expect free samples to do a lot of the persuading.

That night, Arooga's at 1 West Main Street in Patchogue throws its tenth anniversary party. Doors at 9 p.m., two DJs until 2 a.m., and a capped guest list, so the RSVP is not optional decoration. Ten years on downtown Patchogue's busiest corner is genuinely rare, and the bar is celebrating it the way it earned it: as a dance party.

Saturday on the water: oysters in Port Jefferson, a free harbor day in Oyster Bay

The Suffolk County Oyster Jamboree and Frolic runs 11 a.m. to 6 p.m. at Harborfront Park in Port Jefferson, presented by the county's 250th anniversary committee with the village. The pitch is simple: locally harvested oysters from Long Island growers, live music, marine education and colonial-era demonstrations, all in a park that sits directly on the harbor. If the weather breaks wrong, the rain date is Sunday, August 16. Oysters built this county's economy once, and a day built around meeting the people growing them again is the right kind of history lesson.

Across the Sound side in Nassau, the Town of Oyster Bay holds Long Island Sound Exploration Day at the Waterfront Center, 1 West End Avenue, from 10 a.m. to 2 p.m. Admission is free, parking is free at Beekman Beach, and the program is the kind of thing families usually pay for: boat rides and kayak tours first come first served, fishing lessons, bird walks and hands-on science tables from New York Sea Grant and the DEC. Four hours, zero dollars, and your kid comes home having touched something that lives in the Sound.

Riverhead is double-booked, and you can honestly do both

The Polish Town Fair takes over the Pulaski Street neighborhood on Saturday and Sunday, rain or shine, as it has every August since 1975. Saturday opens at 10 a.m. with both anthems, polka holds the main stage from 10 to 5, and the centerpiece lands at noon: the staged Polish Wedding, followed by a parade from St. Isidore's Church to the civic association grounds. The pierogi eating contests run at 1 p.m. for the men and 1:30 for the women, both days. It is the single most specific street fair on Long Island, and it knows it.

Six miles up Sound Avenue, the Hallockville Hootenanny runs noon to 7 p.m. at Hallockville Museum Farm, 6038 Sound Avenue, with five bands, food trucks, craft vendors and no admission charge at all, thanks in part to a Suffolk County grant. The farm is a 28-acre preserved homestead in the middle of the North Fork farm belt, which makes it the prettiest free venue in the county this weekend. Polka until three, hootenanny until seven is a completely defensible Saturday.

Bluegrass at Tanner Park, and the last night of Westbury's feast

The 24th annual Long Island Bluegrass and Roots Music Festival runs noon to 7 p.m. Saturday at Tanner Park in Copiague, presented by the Babylon Citizens Council on the Arts with the Town of Babylon. The headliner is the bluegrass laboratory led by Andy Falco, the Long Island guitarist from the Grammy-winning Infamous Stringdusters, which is about as good as this genre gets within walking distance of the Great South Bay. Per the arts council's announcement, general admission is 20 dollars, kids 11 and under are free, and there are workshops and an open jam area for anyone who brings an instrument.

In Westbury, the Maria SS. Dell'Assunta Society's Feast of the Assumption reaches its 115th final night on Saturday, which is the Feast of the Assumption itself on the Catholic calendar. Mass at St. Brigid's on Post Avenue at 5 p.m., then the procession with the statue of the Blessed Mother through the village streets to the feast grounds at 101 Maple Avenue, where the food, games and music run 6 to 11. The society has been doing this since a band and a borrowed pickup truck in 1910, and the final night is the one with the weight, and the fireworks reputation, on it.

If you can only do one thing

Families west of the Nassau line: Oyster Bay in the morning, Westbury at night, and you never touch a parkway eastbound. Anyone mid-island: Copiague for the bluegrass, which is the best music-per-dollar on this list. East of the William Floyd: Riverhead, both stops, in either order. And if Saturday defeats you, the Polish Town Fair runs again Sunday, pierogi contests included.