A power outage struck most of Middleboro and parts of Lakeville on Tuesday, June 24 — the hottest day of the year so far.

The outage began shortly before 5 p.m., according to Middleboro officials. Around that time, temperatures had reached the high 90s, according to the National Weather Service.

Due to the dangerous heat, Middleboro immediately opened Nichols Middle School as a cooling center. Pets were allowed inside the facility. The town also kept the public library open until 11 p.m. Tuesday as a second cooling location.

In Lakeville, the outage affected a smaller portion of residences, but people still used the town’s cooling center at the Council on Aging.

By about 7:30 p.m., Lakeville Fire Chief Michael O’Brien said the department had received five inquiries about the cooling station. During a Tuesday night Select Board meeting at the Council on Aging, Chair Maureen Candito said affected areas included Pickens Street and Kingman Street. The Lakeville Public Library and Transfer Station also lost power.

Earlier in the day, the Lakeville Fire Department reported responding to eight heat-related emergencies. In Middleboro, the fire department was late to a public event due to a high volume of calls, though it was unclear whether they were heat-related.

Middleboro Town Manager James McGrail said the outage was caused by a transformer issue, not a grid problem.

“We do not have an estimate for when power may be restored, so we are encouraging any residents who need to cool off to visit the middle school or the library,” McGrail said in a statement Tuesday night. “We’re also encouraging all residents to stay hydrated today and to take basic precautions against this potentially dangerous heat.”

Middleboro officials joined residents at the Nichols Middle School cooling station, while Lakeville officials were already present at their town’s cooling center due to a previously scheduled meeting.

Middleboro had ambulances on standby and provided food and bottled water. Police and fire departments in both towns offered rides to their respective cooling centers.