This Weekend's 5K: Leprechauns Run Through the Streets of Somerville

There will be a field of serious runners, and behind them thousands of runners dressed in green, many decked out in shamrocks, with a few leprechauns thrown into the mix.

When the running is done, the crowd will pour into bars in Davis Square and around Somerville for post-race celebrations.

It's the Rás na hEireann, the Race of Ireland, a 5-kilometer road race that takes place every year around Saint Patrick's Day.

According to Paul Collyer, a race organizer, 5500 race bibs have been sold this year, meaning the race is sold out. Somewhere between 4000 and 4800 runners are expected to participate (some people purchase bibs and don't show up). "I've been selling these tickets since August," he said.

This year marks the 10th anniversary of the Rás, which shares a name with a sister race in Ireland near Drogheda. The Irish version of the race is routed around the site of the Battle of the Boyne, fought in 1690 in County Meath, according to Collyer.

"A representative comes from that road race every year," he said. "Our race has really gotten to be big."

The Somerville version of the race is a major sponsor of the Irish Film Festival, which will be coming to Somerville at the end of the month. It also benefits the Somerville High School Track PAC, the football team, the soccer team, the Medford High School track and field team, the Wakefield High School tack and field team, the Breast Cancer Fund, the Boston Triathlon Team and Luna Chix.

What's more, 17 pubs in Somerville and Cambridge are sponsors of the race, "and they're jam-packed all day," said Collyer.

The race begins in Davis Square, but pubs in Ball Square, Magoun Square, Teele Square and Inman Square are part of the festivities. Collyer was thrilled some Cambridge bars were joining the fun, such as the Druid and Joe Sent Me. "We're driving the boat, and Cambridge is the passenger," he said, showing some good-humored Somerville pride.

At the moment, the weather forecast is for sunny skies and temperatures in the mid 60s, but the weather doesn't matter said Collyer, adding, "There's an old Irish saying: It doesn't rain in the pubs."

The race begins at 11 a.m. in Davis Square.