Miami averages about 69°F (20.5°C) in January. International Falls, Minnesota averages about 4°F (-15°C) the same month, a gap of roughly 65 degrees inside one country. The United States covers a wider range of climates than almost any nation on Earth, and that range does more than decide what people wear outside. It changes how long they live, and in which month they are most likely to die.
Key Takeaways
January is the deadliest month in 39 of the 50 states, according to CDC mortality data.
Cardiac deaths in the U.S. peak around December 25 and January 1 each year.
Eight states, including Arizona, Hawaii, and Washington, peak in February instead.
Idaho and Montana are the only states where March is deadliest.
Alaska is the only state where December outranks every other month.
Cold weather asks more of the heart. Blood vessels constrict in low temperatures, blood pressure climbs, and a heart that already struggles with disease has to push harder against that resistance. A study in the AHA’s own journal Circulation found more cardiac deaths occur in the U.S. on December 25 than on any other day of the year, with December 26 and January 1 close behind.
Flu and pneumonia add to the toll. Respiratory infections spread faster indoors, where people gather during cold months, and hit older adults and anyone with an existing heart or lung condition hardest.
In 2017, the U.S. averaged 7,708 deaths a day. January’s daily average reached 8,478, ahead of February at 8,351 and December at 8,344. The quietest months were June, July, and August, each averaging under 7,300 deaths a day.
Where Other Months Take Over
Eight states peak in February instead of January, and they don’t share one explanation. Arizona, Colorado, New Mexico, and Oklahoma belong to the Mountain West, Southwest, and southern Plains. Oregon and Washington cover the Pacific Northwest. West Virginia is in Appalachia, and Hawaii is the only tropical state with a winter peak at all. Temperature alone doesn’t explain the group. Flu season may explain it better. It crests in February in some years rather than January.
Idaho and Montana are the only states where March claims the top spot. Both are lightly populated relative to their land area, which makes a single month’s death count more sensitive to swings from one year to the next. Elevation may also play a role. Mountain winters in the northern Rockies often peak later than the calendar-driven cold of the Midwest and Northeast.
Alaska stands alone with December. Its winter starts earlier and hits harder than anywhere else in the country, and the toll shows up before the calendar reaches January.
