Summer daily high and Winter nightly low
Where Summer daily high is higher, Winter nightly low tends to be higher. The link is strong: +0.64 across 3,120 counties, on a scale from −1 (opposite) to +1 (in step). That figure compares places with the same population density, income and education, so those differences can't explain it. It holds inside states too. Measured separately within each of 40 states, the middle value of the link is +0.66.
Holds after adjusting
Every place, plotted
One dot for each place reporting both measures. Hover over or tap a dot to see its name and values. The thin line is the straight line that best fits the dots. The bold line, shown for counties, is the link after adjusting for density, income and education. A dot far from the lines is a place that does not follow the pattern.
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What each measure is
Summer daily high
The average daily high temperature in June, July and August, in degrees Fahrenheit, across the whole county or state. It shows how hot summer afternoons are.
NOAA NCEI nClimDiv · NOAA NCEI nClimDiv climdiv-tmaxcy/tmaxst
Winter nightly low
The average nightly low in winter, in degrees Fahrenheit, across the whole county or state. Winter here means December of the year before, then January and February. So the winter of 2024 to 2025 is listed under 2025.
NOAA NCEI nClimDiv · NOAA NCEI nClimDiv climdiv-tmincy/tminst
Highest and lowest
Where each measure is highest and lowest among the places reporting both (2023), with the other measure beside it. This is shown for every size of place where both are published. Metro-area values are added up from their counties. A measure that cannot be added up across counties, such as a middle value (median), has no metro figure. Counts are shown per 1,000 residents, since raw totals would only list the largest places. Cities and towns and ZIP codes are shown where the Census survey or the CDC publishes them; most other sources stop at the county. They are shown for places of 5,000 residents or more, and only where the survey’s margin of error is small enough for the figure to be usable. The CDC publishes its health estimates for cities in a version adjusted for age, so places with older or younger people can be compared fairly, but not for ZIP codes.
Counties
By summer daily high
| Summer daily high | Winter nightly low | |
|---|---|---|
| Highest | ||
| Imperial County, CA | 106 | 44.5 |
| Yuma County, AZ | 106 | 41.8 |
| La Paz County, AZ | 105 | 40.4 |
| Maricopa County, AZ | 104 | 39.9 |
| Ward County, TX | 103 | 36 |
| Lowest | ||
| Aleutians West Census Area, AK | 53.7 | 28.4 |
| Skagway Municipality, AK | 54 | 12 |
| Yakutat City and Borough, AK | 54.2 | 16.5 |
| Juneau City and Borough, AK | 54.9 | 16.1 |
| Chugach Census Area, AK | 54.9 | 15 |
By winter nightly low
| Summer daily high | Winter nightly low | |
|---|---|---|
| Highest | ||
| Honolulu County, HI | 82 | 66 |
| Kalawao County, HI | 81.6 | 63.6 |
| Monroe County, FL | 91.9 | 63.2 |
| Miami-Dade County, FL | 92.1 | 62.2 |
| Kauai County, HI | 80.5 | 62 |
| Lowest | ||
| North Slope Borough, AK | 57.6 | -13.1 |
| Yukon-Koyukuk Census Area, AK | 65.9 | -7.5 |
| Southeast Fairbanks Census Area, AK | 65.9 | -6.8 |
| Northwest Arctic Borough, AK | 60.6 | -6 |
| Fairbanks North Star Borough, AK | 68.1 | -4.1 |
States
By summer daily high
| Summer daily high | Winter nightly low | |
|---|---|---|
| Highest | ||
| Texas | 98.3 | 39 |
| Louisiana | 95.7 | 46.5 |
| Arizona | 94.8 | 29.6 |
| Mississippi | 93.2 | 42.5 |
| Oklahoma | 93 | 30 |
| Lowest | ||
| Alaska | 60.6 | 1.5 |
| Maine | 73.7 | 14.9 |
| Vermont | 75.3 | 17.5 |
| New Hampshire | 75.5 | 18.8 |
| Hawaii | 76.3 | 57.4 |
By winter nightly low
| Summer daily high | Winter nightly low | |
|---|---|---|
| Highest | ||
| Hawaii | 76.3 | 57.4 |
| Florida | 92.7 | 52.2 |
| Louisiana | 95.7 | 46.5 |
| Mississippi | 93.2 | 42.5 |
| Alabama | 90.9 | 41.9 |
| Lowest | ||
| Alaska | 60.6 | 1.5 |
| North Dakota | 80.6 | 2.47 |
| Minnesota | 79.9 | 5.27 |
| Wyoming | 76.7 | 9.07 |
| South Dakota | 83.6 | 9.3 |
Metro areas
By summer daily high
| Summer daily high | Winter nightly low | |
|---|---|---|
| Highest | ||
| El Centro, CA | 106 | 44.5 |
| Yuma, AZ | 106 | 41.8 |
| Phoenix-Mesa-Chandler, AZ | 104 | 39.1 |
| Zapata, TX | 103 | 51.9 |
| Eagle Pass, TX | 103 | 45.4 |
| Lowest | ||
| Juneau, AK | 54.9 | 16.1 |
| Anchorage, AK | 57.3 | 6.75 |
| Ketchikan, AK | 60.7 | 23.3 |
| Breckenridge, CO | 67.5 | 5.62 |
| Fairbanks-College, AK | 68.1 | -4.1 |
By winter nightly low
| Summer daily high | Winter nightly low | |
|---|---|---|
| Highest | ||
| Urban Honolulu, HI | 82 | 66 |
| Key West-Key Largo, FL | 91.9 | 63.2 |
| Kapaa, HI | 80.5 | 62 |
| Kahului-Wailuku, HI | 79.7 | 61.7 |
| Miami-Fort Lauderdale-West Palm Beach, FL | 92.6 | 60.9 |
| Lowest | ||
| Fairbanks-College, AK | 68.1 | -4.1 |
| Grand Forks, ND-MN | 79.8 | 0.408 |
| Bemidji, MN | 77.2 | 1.53 |
| Fargo, ND-MN | 81.4 | 1.59 |
| Jamestown, ND | 79.7 | 1.7 |
Counties furthest from the pattern
Compared with the straight line that best fits all 3,143 counties: the five with far more winter nightly low than their summer daily high would suggest, and the five with far less.
| Summer daily high | Winter nightly low | |
|---|---|---|
| Above the line | ||
| Honolulu County, HI | 82 | 66 |
| Maui County, HI | 79.7 | 61.7 |
| Kalawao County, HI | 81.6 | 63.6 |
| Kauai County, HI | 80.5 | 62 |
| Hawaii County, HI | 73.7 | 54.2 |
| Below the line | ||
| Pierce County, ND | 80.4 | -1.23 |
| Bottineau County, ND | 80.4 | -0.767 |
| Towner County, ND | 79.5 | -1.57 |
| McHenry County, ND | 81.2 | 0.567 |
| Benson County, ND | 79.7 | -0.867 |
Two series, one county
Both measures over time for a county you pick. The two charts are stacked, so they share only the years along the bottom. You can pick from the thirty largest counties reporting both. This panel covers 2010–2024, and a measure published only once shows as a single dot.
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Every version of the link
Each row measures the same link, from −1 to +1, in a different way. If the rows mostly agree, the link does not depend on one choice of method.
| Before adjusting for anything | +0.641 | 3,120 counties reporting both |
| After adjusting for density, income and education | +0.635 | the part of the link that is not just how urban, rich and educated a place is |
| Also adjusting for population size | +0.635 | size taken out as well as density |
| Also comparing only within each state | +0.406 | each county is compared only with others in its own state, so this is no longer a comparison between states |
| Giving bigger counties more weight | +0.620 | the adjusted link for the average resident rather than the average county. With this weighting, the data counts for about 287 equally weighted counties |
| Middle value inside single states | +0.662 | the link worked out inside each of 40 states with at least 20 counties reporting |
| Using ranks, after adjusting | +0.712 | uses each county’s rank, not its value, so a few extreme counties cannot create the link |
How much to believe it
Could it be chance?
The p-value is the chance of seeing a link this strong if there were really none. A value of 0.05 or less means the link is unlikely to be chance. Very small values are written in short form: 3.1e-16 means 0.00000000000000031, and the bigger the number after “e-”, the smaller the value. Treating every county as a separate case gives p = 0.000. But counties in the same state tend to resemble each other, so the better figure allows for that: p = 3.4e-8. The site tested 24,090 pairs, and testing so many turns up some flukes. The q-value allows for that too. For this pair it is 0.000.
Do nearby places look alike?
Moran’s I measures how much nearby places look alike: 0 means no map pattern, and higher means neighbours are more similar. For the part of each county that the adjustment leaves unexplained, it is +0.77 (p = 0.001). That unexplained part still clusters on the map. So some regional factor shared by both measures is not accounted for.
Did they change together?
The figures above compare counties at one moment. This asks a different question: where summer daily high rose most, did winter nightly lowmove too? Each county’s change is compared with the average change in its own state. That takes out ups and downs that hit a whole region at once. Each change is the gap between two estimates that both contain some error. That error pulls these links towards zero, so a weak one is weak partly for that reason. The q column shows whether a link could be a fluke, allowing for the many pairs tested: 0.05 or less means it is unlikely to be chance.
| Period | Counties | Change together | Within states | q |
|---|---|---|---|---|
| 2014–2019 the main test: each Census survey figure averages five years, and these two do not overlap; before the pandemic | 3,143 | +0.19 | -0.02 | 0.892 |
| 2019–2023 a repeat check: its two five-year survey figures both include 2019, and it covers the COVID years | 3,143 | -0.03 | +0.16 | 0.057 |
Over the main period, any link between the changes could easily be chance. How change is measured.
Related pairs
- Average temperature and Winter nightly low — +0.91
- Average temperature and Summer daily high — +0.88
- Loneliness and Winter nightly low — +0.58
- High cholesterol and Winter nightly low — +0.55
- Adults under 65 without health insurance and Summer daily high — +0.53
- Returns claiming the earned income credit and Winter nightly low — +0.51
- High blood pressure and Winter nightly low — +0.50
- Food insecurity and Winter nightly low — +0.50
Association only. Nothing here shows that either measure changes the other. This describes counties, not the people in them. Two measures going together across places does not mean the same people have both. How the US county data works · Explore Summer daily high and Winter nightly low