Tim Walz returns to Boston on Wednesday. Here’s what you need to know.

Vice presidential candidate Tim Walz will speak at the 57th International Association of Fire Fighters convention in Boston on Wednesday morning.

Walz will speak before one of the largest unions in North America, representing nearly 350,000 firefighters, emergency responders and paramedics in the United States and Canada.

“Governor Walz, himself a former union member, has a strong track record of defending unions and standing up for workers—from joining the picket line and passing the most pro-worker bill package in Minnesota history to guaranteeing Minnesota workers [are] “paid sick, medical and family leave,” a statement from the Harris-Walz campaign said.

The 57th convention, which will be held at the Boston Convention & Exhibition Center in the Seaport from August 25-30, will be Walz’s second appearance in Boston in two weeks, following his three-day solo tour that included an appearance at a fundraiser in the Back Bay on August 14.

Walz also stopped in Newport, Rhode Island, where the Catholic university that hosted the event has been criticized by the Diocese of Providence for the decision.

Vice President Kamala Harris and her husband Doug Emhoff have also made recent appearances in Massachusetts, Harris in Pittsfield after launching her own presidential campaign, and Emhoff in Martha’s Vineyard.

Governor Maura Healy opened the firefighters convention, calling for national unity.

“We can feel divided as a nation, sometimes we don’t agree on everything, but today I want to highlight the importance of fostering national unity, and the firefighters’ commitment to service, community and country is a powerful example and something we can all unite around,” she said.