If cold is much more dangerous than warmth, why should we be afraid of a little extra warmth?

How Does a Heat Wave Affect the Human Body?: Scientific American

Extreme heat is only blamed for an average of 688 deaths each year in the U.S., according to the Centers for Disease Control and Prevention (CDC)...I think it's always been a problem. There's history over hundreds of years of people dying of heat. Philadelphia in 1776 had a major heat wave that caused deaths. 

2007: Economists: extreme cold weather costly, deadly

BERKELEY -- Fatalities in the continental United States tend to climb for several weeks after severe cold spells, ultimately numbering 360 per chilly day and 14,380 per year, according to a new study co-authored by a University of California, Berkeley, economist.

Deaths linked to extreme cold account for 0.8 percent of the nation's annual death rate and outnumber those attributed to leukemia, murder and chronic liver disease combined, the study reports. Cold-related deaths also reduce the average life expectancy of Americans by at least a decade, it says. [Huh?]

The numbers are "remarkably large," said Enrico Moretti, a UC Berkeley associate professor of economics, and Oliver Deschenes, an associate professor of economics at UC Santa Barbara, in a December 2007 working paper, "Extreme Weather Events, Mortality and Migration."

The study also says that demographic shifts from colder climes to warmer ones -- for reasons such as better jobs, cheaper housing and sunshine - appear to delay an estimated 4,600 deaths a year. The researchers also said that over the past 30 years, longevity gains associated with geographic mobility accounted for between 4 and 7 percent of the increases in life expectancy in the United States.