The mountain resort town of Aspen, Colorado, is part of a real-estate trend playing out in places such as New York’s eastern Long Island shore and in Lake Tahoe, Calif., where home prices have surged as wealthy urbanites look for space and outdoor amenities during the pandemic and while working from home.

Aspen is attracting affluent buyers from both coasts and Texas. July home-sales contracts jumped more than fivefold over that same month a year earlier, a surge that appraiser Jonathan Miller called unprecedented for Aspen in a recent report.

August sales were more modest, but the number was still double what it was for that month last year. More than half of the 145 home sales in July sold for better than $20 million, solidifying Aspen’s status as a luxury real-estate hot spot.

Covid-19 cases haven’t significantly risen with Aspen’s new arrivals, even though ski resorts were considered superspreader sites early in the pandemic.

Stephen Smith, a money manager and owner of semiprivate plane company Wildcat Touring, said his summer-only service connecting Aspen to Dallas and Houston is having its best-ever year. He owns a home in Aspen and said he is considering expanding into fall or winter service. “Everyone’s fleeing the cities to get some clean air,” Mr. Smith said. The Aspen School District received 150 new enrollment requests in August, five times more than this town of about 7,400 would see in a typical year.

Eight-hundred square-foot Victorian cottages on lots that once housed miners now sell for several million dollars. Buyers sometimes spend millions more to build modern attachments, often adding large basements. The ability to build below ground level is especially attractive to pandemic buyers, many of whom are looking for extra space to work from home.