The Coldest Day of the Year, City by City

The Exact Coldest Date for Every Major City

Ordered from the earliest coldest day to the latest — which also walks you from the West Coast to the Northeast. The “average low” is the smoothed day-of-year mean low at each city's primary long-record airport station, 1970–present. “Weeks after solstice” is measured from December 21.

Dates are the bottom of a centered 7-day smoothed average, not a single record-cold day, so they are stable rather than driven by one Arctic outbreak. Values reflect 1970–present, so a warming trend nudges the averages up slightly versus older normals. Look up any single date's actual history in Chicago, Denver or Los Angeles on its city page.

Why the Coldest Day Trails the Shortest Day

The winter solstice, around December 21, is the shortest day — the least incoming sunlight of the year. You might expect that to be the coldest day. But temperatures keep sliding for weeks afterward, because the ground, the air and the oceans are still losing more heat to space each day than the weak winter sun puts back. Only when the days have lengthened enough to balance that loss does the average finally bottom out and start to climb. Meteorologists call the gap seasonal lag — the same reason the hottest day of summer comes well after the June solstice.

The twist in winter is that a second force sets the timing in much of the country: outbreaks of Arctic air. According to NOAA's National Centers for Environmental Information, the eastern and central US reaches its coldest point in January largely because that is when frigid air chilled over Alaska and Canada plunges south most often, reinforced by fresh snow cover that reflects sunlight away. West of the Rockies, those mid-winter Arctic plunges are far less common — the Pacific keeps feeding in milder, cloudier air — so the West tracks the solar cycle instead and bottoms out in late December. That single difference is why the coldest day splits so cleanly between the two halves of the country.

The Two Americas of Deep Cold

Sort the cities by date and the country falls into two timing zones, with the dividing line running roughly down the Continental Divide — exactly where NOAA's own coldest-day map draws it.

The West Coast Does Cold and Heat Exactly Backward

Here is the finding no listicle mentions. Set this page next to our hottest day of the year analysis and the West Coast flips completely. For heat, the Pacific coast peaks last — Los Angeles' hottest day, on average, is September 4, weeks after the interior has cooled. For cold, the same coast bottoms out first — Los Angeles' coldest day is December 29. Same city, same ocean, opposite timing: its warmest and coldest days are about ten weeks apart from where the inland rule would put them, and in opposite directions.

The reason the two lags point opposite ways is that different forces set them. Summer's lag on the coast is long because the ocean warms so slowly it keeps dragging the warmest days into early fall. Winter's “lag” on the coast is short because the thing that makes the East coldest in January — Arctic air — barely reaches the Pacific coast at all, so nothing pushes its minimum past the solar low in late December. The interior, by contrast, is roughly symmetric: Chicago peaks around July 17 and bottoms out around January 17, four weeks after each solstice, like clockwork.

So What's the Coldest Month?

Zoom out from the single coldest day to the coldest month and the answer simplifies: January, for almost everyone. In our station data January is the coldest calendar month in 37 of these 41 cities. The only exceptions are, predictably, on the West Coast — Seattle, San Diego, Las Vegas and Sacramento run a hair colder in December, because their whole cold season is shifted so early. So “the coldest month” is January nearly everywhere, and the places where December edges it out are the same places whose single coldest day also breaks the mid-January rule.

Is the Coldest Day Getting Less Cold?

Yes. Because this climatology uses 1970–present data, the average lows above already run warmer than the older 20th-century normals, and winter nights have warmed faster than summer days across most of the country. NOAA's own analysis has found the coldest stretch of the year drifting slightly later in parts of the East as well. The same warming shows up at the opposite end of the calendar — the first fall frost now arrives up to 17 days later than it did in the 1970s. If you want the all-time floor rather than the average, our coldest temperatures ever recorded breakdown covers the records, and the coldest cities in America ranks who is coldest overall. For how each state stacks up year-round, see average temperature by state.

How We Computed This

For each city we selected its primary long-record NOAA GHCN-Daily airport station — O'Hare for Chicago, Logan for Boston, Sacramento Executive for Sacramento, and so on, excluding nearby co-op and hilltop sites that bias cold. Daily low temperatures (stored in tenths of a degree Fahrenheit) were averaged by calendar date across all years from 1970 to the present, February 29 excluded and quality-flagged readings dropped. Because a single calendar date has only about 55 years behind it, the raw day-to-day curve is noisy, so we applied a centered 7-day smoothing and took the bottom of that smoothed curve as the “coldest day.” The coldest-month figures come from the same stations, averaging daily lows by calendar month. This is a 1970-present normal, not a full-century climatology, and it reflects the warming of recent decades.

Frequently Asked Questions

Sources & Method

City day-of-year cold climatology: NOAA GHCN-Daily via our database (1970–present), computed as described above. The regional West-vs-East pattern and the Arctic-outbreak explanation follow NOAA NCEI, “When to Expect the Coldest Day of the Year” and NOAA Climate.gov's coldest-day interactive map. Explore records and extremes across the country on our US weather records hub, or look up the weather on any past date in your own city.