Arthur Feldman was almost ready to organize a mothers and childrens' march on Peco's corporate headquarters in Center City when, miraculously, the lights came back on.

Service trucks arrived in his Lower Merion neighborhood Sunday afternoon.

Until then, the Feldman family was among more than 7,000 Montgomery County residents still without power. That means 22 percent of the utility's county customers endured six days or more with no heat or lights, no cellphone chargers, computers, or TVs.

A Peco representative said 90 percent of customers across the greater Philadelphia area who lost power had gotten it back by Saturday, and she expected most of the remaining cases to be fixed by midnight Sunday.

"The customers left without power at this point in time are the most difficult cases that we have," said Karen Muldoon Geus, a Peco spokeswoman.

For the first several days, the Feldmans and some other Lower Merion residents found relief at a hotel in Conshohocken. But when the weekend came, the hotel was booked with weddings and other reservations, so they had to return to their frigid homes.

"We spent the night in our very cold house," said Feldman, the executive dean of the Temple University School of Medicine.

With so many residents still off the grid and overnight temperatures dipping into the 20s, Montgomery County officials declared a "code blue" cold-weather warning, scheduled to continue through noon Monday. Lower Merion, one of the county's hardest-hit townships, set up "warming stations" at local firehouses and libraries to provide residents with a place to warm up, get a cup of coffee and other nourishment, recharge electronic equipment such as cellphones and laptops, and just have an opportunity to get outside and away from home for a bit.

On Sunday afternoon, firefighters at the Narberth station said they were prepared to comfort residents with coffee, snacks, and power adapters. But no one showed up.

Muldoon Geus said 606 Peco customers in Lower Merion were still without power on Sunday afternoon - about 2.7 percent of that service area.

Many of those unlucky customers are victims of what are called "nested outages," areas in which crews fix a primary service problem like downed power lines, but overlook a secondary issue like a blown transformer. In those cases, a handful of customers are left in the dark, watching in dismay as their neighbors' lights flick on.

Often, the utility doesn't know that those customers are still offline. Muldoon Geus said it's important that customers call Peco to get back on the fix-it list.

Staff writers Jeff Gammage and Andrew Maykuth contributed to this story.

Contact Jessica Parks at 610-313-8117 or jparks@philly.com.