Mary Ellen Kreigh, an employee at Frame Woods in downtown Lawrence, was busy Wednesday getting ready for today's annual sidewalk sale, which officially opens at 7 a.m.

Despite sizzling heat, thousands of bargain hunters are expected to swarm downtown Lawrence today for the annual sidewalk sale.

“I think people are insane,” said Melissa Travis, sales associate at Arensberg Shoes, 825 Mass. “They’ll come out for a good sale even if it kills them.”

The forecast is for a high temperature of 104 with the heat index – heat and humidity combined – hitting 113. A heat advisory is in effect through this evening.

Work on Massachusetts Street’s waterlines will be halted. There will be one-way northbound traffic in the 700 and 800 blocks, with no parking on the west side of those blocks. Shoppers should instead seek spaces behind the businesses.

Some shops are taking extra steps to accommodate customers. Arensberg Shoes is among those opening at 6 a.m. instead of 7 a.m. for shoppers wanting to buy before the heat intensifies. Most shops will be open until 8 p.m. or 9 p.m.

Khara Loeppke, assistant manager at Maurices, 739 Mass., said she didn’t expect the heat to deter people.

“There’s hard-core shoppers,” she said. “I don’t think this is going to stop them.”