Summer officially starts on June 20 but, in this town, the season effectively begins this weekend.

Memorial Day kicks off more than three months jam-packed with live music, festivals, baseball, robots (yes, robots) and other community events.

In fact, the town’s population jumps by nearly 20,000 people who will swarm the beaches, businesses and back roads this year.

“The hustle and bustle of everything is pretty great,” said Kat Jones, president of the Onset Bay Association. “The number of people seems to quadruple overnight. They come from all over the place to visit.”

Before the fun begins, members of the Veterans Council on Monday will conduct a solemn morning of remembrance for the fallen. Starting at 8:30 a.m. on the town green on Main Street, veterans will place wreaths on gravestones and monuments throughout town -- concluding at 12:30 p.m. in front of Town Hall.

This weekend marks the return of CapeFLYER passenger train service with Wareham Village being a stop on the Boston-to-Hyannis route.

The train will run every Friday, Saturday and Sunday until Labor Day. Operated by the Massachusetts Bay Transportation Authority, this is the third year the CapeFLYER will make a stop at the station on Merchant’s Way. For schedules and ticket fares, visit www.capeflyer.com.

Whether folks arrive by train or car or live here year-round, they will have a lot to do.

On Saturday, May 28, the OBA’s free concert series starts with a performance by the South Coast Musicians Band & Chorus from 1 to 3 p.m. in the Lillian Gregerman Bandshell in Onset.

Baseball fans will be able to catch Gatemen games starting June 12.

In Wareham, the Gatemen, a part of the amateur Cape Cod Baseball League, take the field for their first home game June 12. The Gatemen play at Spillane Field adjacent to the middle school. First pitch is at 5:30 p.m. For a team schedule, visit www.gatemen.org.

Want to get out on the water while supporting local events? Then a good bet is the annual Kayak Poker Run set for June 25.

Jones said kayakers may bring their own boats or rent from Nemasket Kayak for the fundraiser. The event starts at 9 a.m. at Shell Point and features boaters getting five cards that are then “played” at the end of the day. Whoever has the best hand wins a cash prize.

“We have some of the best kayaking around here, and this is a chance to explore the little nooks and crannies you might not otherwise see,” Jones said.

On the other side of town, the Cranberry Coast Concert’s summer season will kick off its 11th year on July 8 at 7:30 p.m. at 226 Main St. Held Thursdays at either Eastern Bank on Main Street or the First Congregational Church at 11 Gibbs Ave., the concerts are free and start at 7:30 p.m. For a complete schedule, visit www.cranberrycoastconcerts.com.

The Wareham Historical Society also plenty of events planned.

On July 4, society members will hold the 39th Annual Outdoor Antiques Show from 8 a.m. to 2 p.m. at the town green on Main Street.

July 23 will bring the return of the second annual Onset Music Festival. Hosted by Wareham singer-songwriter Grace Morrison, the show will feature performances by a variety of local musicians.

Aug. 6 will bring the 24th annual Onset Blues Festival. Jones said the show is one of the association’s major fundraisers. For tickets, visit www.onsetbluesfestival.com.

Even though the annual Onset fireworks will not light up the skies this year, events are still planned for Independence Day.

The third annual Onset Bay Blessing of the Fleet is scheduled for Saturday, July 2. The event starts at 10:30 a.m. with the vessel parade setting sail at 11 a.m. Visitors may watch from Onset Pier.

Each vessel in the parade will be blessed by a priest. All mariners are encouraged to decorate their boats.

Following the blessing, more activities will be offered at the pier from 11 a.m. to 2 p.m., including parades for pets, bicycles and doll carriages.

Also on July 2, the nonprofit Cultural Connections will co-sponsor the Wareham Rocket & Robotics Festival starting at noon in Lopes Field in Onset.

Details are still being worked out, but attendance is a suggested $3 donation and free rockets will be handed out to the first 100 kids.

The third annual Chalk Full of Fun Street Painting Festival is set for Aug. 27 from 10 a.m. to 6 p.m. For a small fee, residents will receive chalk to decorate the sidewalks leading up to that evening’s Illumination Night.

“That has a hundred year history in Onset,” said Jones. “It’s one of my favorites.”

For the event, red flares are placed all around the water’s edge, illuminiating the bay for about 30 minutes after sunset. The night will also feature live music and a fire dancer.

With those, and many more, events on the schedule, Jones said there’s plenty of reasons to make the town a summer destination.

“It’s a tradition to come to Onset,” she said. “It’s a happening little place.”