Hot town, summer in the city? No kidding.

The high temperatures blanketing the Northeast and mid-Atlantic regions of the country are making many people miserable, but those in New York City, Philadelphia and other dense, built-up areas are getting hit with the heat in a way their counterparts in suburbs and rural areas aren't.

Cities absorb more solar energy during the day and are slower to release it after the sun sets, making for uncomfortable nights and no real relief from the heat. And because they haven't cooled down as much overnight, mornings are warmer and the thermometer goes right back up when the sun starts beating down the next day.

Scientists have known for years about so-called heat islands, urban areas that are hotter than the less-developed areas around them. Cities are just "not well designed to release that summertime heat," said William Solecki, geography professor at Hunter College and director of the City University of New York's Institute for Sustainable Cities. [ ASSOCIATED PRESS ]