Clear days
The number of days in the year when clouds blocked less than 7% of the sunlight, so the ground got at least 93% of what a cloudless sky would give. It is the closest measure here to a count of sunny days. It is a NASA estimate from weather satellites for squares of land about 60 miles across, not a count by someone watching the sky, and nearby counties often share a value. The 93% line was chosen so that, on average, the count matches NOAA's counts of clear days at 64 weather stations. There, a clear day is one with three tenths of the sky or less covered by cloud in daylight. It starts in 2001, since the older satellites count clear days differently.
Reported for3,144areas, in 51 states — none in PR
Link to density0.28not mostly about how urban a place is
Nearby places alike0.91Moran’s I: strongly, neighbouring places tend to be similar
Typeratedays
How it has moved
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Every state, every year
One row per state and one column per year, sorted by the latest value. It shows states, not counties: nobody can scan 3,222 rows, and the pattern only shows when it all fits on one screen.
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Where it comes from
NASA POWER (Prediction Of Worldwide Energy Resources) · NASA POWER daily regional API, community RE, ALLSKY_SFC_SW_DWN / CLRSKY_SFC_SW_DWN
Days in the year when clouds blocked less than 7% of the sunlight, from satellites. Combined areas are weighted by their people.
Combining areas: an average weighted by SUN.POPULATION.
What it goes with
The strongest links that have a page of their own. Unadjusted is the link before adjusting for anything, from −1 (opposite) to +1 (in step). Adjusted compares places with the same population density, income and education levels, so those differences can’t explain the link. This list leaves out the 3 pairs built from the same numbers or the same model as this measure, since they are bound to match.
| Measure | Unadjusted | Adjusted |
|---|---|---|
| Clear days and Summer daily highWhere Clear days is higher, Summer daily high tends to be higher: a strong link that holds when only places with similar density, income and education are compared, and inside states as well. Summer daily high by US county | +0.72 | +0.77 |
| Clear days and Days of 90°F or hotterWhere Clear days is higher, Days of 90°F or hotter tends to be higher: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Days of 90°F or hotter by US county | +0.62 | +0.64 |
| Clear days and Average temperatureWhere Clear days is higher, Average temperature tends to be higher: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Average temperature by US county | +0.46 | +0.59 |
| Clear days and Cooling degree daysWhere Clear days is higher, Cooling degree days tends to be higher: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Cooling degree days by US county | +0.51 | +0.58 |
| Clear days and Wet daysWhere Clear days is higher, Wet days tends to be lower: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Wet days by US county | -0.60 | -0.57 |
| Clear days and Heating degree daysWhere Clear days is higher, Heating degree days tends to be lower: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Heating degree days by US county | -0.37 | -0.56 |
| Clear days and Share Hispanic or Latino, any raceWhere Clear days is higher, Share Hispanic or Latino, any race tends to be higher: a moderate link that holds when only places with similar density, income and education are compared. Share Hispanic or Latino, any race by US county | +0.48 | +0.49 |
| Clear days and Freezing daysWhere Clear days is higher, Freezing days tends to be lower: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Freezing days by US county | -0.27 | -0.48 |
| Clear days and Longest dry spellWhere Clear days is higher, Longest dry spell tends to be higher: a moderate link that holds when only places with similar density, income and education are compared, and inside states as well. Longest dry spell by US county | +0.49 | +0.48 |
| Clear days and Adults under 65 without health insuranceWhere Clear days is higher, Adults under 65 without health insurance tends to be higher: a moderate link that holds when only places with similar density, income and education are compared. Adults under 65 without health insurance by US county | +0.46 | +0.44 |
15 more pairs with clear days have a page: Colorectal cancer screening · Area in drought · Current asthma · Weeks with half the area in drought · People per tax return · Cancer other than skin cancer · Share White, not Hispanic · Medicare spending per enrollee · Arthritis · Winter nightly low · Share foreign-born · Yearly precipitation · Expected yearly tornado loss · Religious adherents · Burglary rate.
Population makeup
How this measure varies with the racial and ethnic makeup of counties. Every group is shown, whatever its rank. These are links across counties: they describe places, not people. They say nothing about any person’s risk or behaviour based on their race. Counties with a larger share of one group also differ in much else, such as income, segregation, region and history. The adjusted figure only accounts for density, income and education.
| Share of residents | Unadjusted | Adjusted |
|---|---|---|
| Clear days and Share White, not HispanicWhere Clear days is higher, Share White, not Hispanic tends to be lower: a weak link that holds when only places with similar density, income and education are compared, and inside states as well. Share White, not Hispanic by US county | -0.33 | -0.38 |
| Clear days and Share Black, not HispanicWhere Clear days is higher, Share Black, not Hispanic tends to be higher: a weak link that holds when only places with similar density, income and education are compared. Share Black, not Hispanic by US county | +0.11 | +0.13 |
| Clear days and Share Hispanic or Latino, any raceWhere Clear days is higher, Share Hispanic or Latino, any race tends to be higher: a moderate link that holds when only places with similar density, income and education are compared. Share Hispanic or Latino, any race by US county | +0.48 | +0.49 |
| Clear days and Share Asian, not HispanicCould easily be chance once only places with similar density, income and education are compared. Share Asian, not Hispanic by US county | -0.06 | +0.04 |
| Clear days and Share American Indian or Alaska Native, not HispanicCould easily be chance once only places with similar density, income and education are compared. Share American Indian or Alaska Native, not Hispanic by US county | -0.06 | -0.09 |
Highest and lowest
Of 3,144 counties reporting it. These are the two ends of a national ranking. For most measures, that ranking mostly sorts places by income and how urban they are. That is why the place pages compare each place with similar places instead.
Highest
- Yuma County, AZ — 273
- La Paz County, AZ — 272
- Imperial County, CA — 258
- Maricopa County, AZ — 254
- Pinal County, AZ — 236
The middle area reports 118. The middle half of counties falls between 97 and 133 (the 25th to 75th percentile).
US Counties With the Highest Clear Days · US Counties With the Lowest Clear Days
All measures · Explore its pairs · How the US county data works