The first ever image of the heat islands created by Minneapolis and St. Paul were posted last week by atmospheric scientists at the University of Minnesota. The map was created on Sept. 15 at 4 a.m., and it shows a temperature range of 11.3 degrees Fahrenheit. Apple Valley was cool -- Golden Valley was warm.

Peter Snyder, University of Minnesota

They are embarking on a research project to study urban heat islands to figure out how to reduce energy use and protect human and animal health. Professors Peter Snyder and Tracy Twine plan to put 200 temperature sensors around the Twin Cities in grassy back yards and down towns. The thermometers will measure temperature every few minutes for the next four years, and show where the warmest and coolest spots are, and where and how temperatures move.

Eventually the researchers hope to do the same on up to 200 cities. It could lead to changes in how cities look. Some places, for instance, already promote heat reflecting white roofs and tree shaded parking lots.