By the end of the century, the Twin Cities area could see eight times as many deaths annually due to extreme heat as it does now, according to a study by the Natural Resources Defense Council (NRDC). The projected increase -- from about 14 per year to 121 by century's end -- would be among the steepest experienced by 40 major metro areas. The authors said that is partly because extremely oppressive heat waves would be more of a shock to northern residents' systems.