8.2 usable nights
5–11 in the middle half of years · 3.1 typically near a dark moon.
310 astronomical-dark hours in an average month
20-year trip-planning baseline
Best time to stargaze at Key West
March: 14.3 usable nights on average. Use this seasonal climate baseline to choose a month, then use the live forecast to choose a night.
Site darkness · modelled, not measured
Brightened skyBortle classes describe observed sky conditions; this brightness model does not establish a measured Bortle class.20.5–21.0 mag/arcsec²
The short answer
March has been strongest.
It averages 14.3 usable nights, versus 3.2 in August. A typical March lands between 11 and 17 usable nights.
Record2005–2024 · 20 complete years
Usable nightAt least 3 astronomical-dark hours and NASA POWER nighttime cloud ≤30%
Dark-moon nightUsable night with ≤25% illumination at local solar midnight
ResolutionCERES SYN1deg 1° cloud grid; regional climate, not a campsite guarantee
Seasonal fingerprint
Usable nights by month
Month by month
12.9 usable nights
10–17 in the middle half of years · 4.3 typically near a dark moon.
283 astronomical-dark hours in an average month
14.3 usable nights
11–17 in the middle half of years · 4.6 typically near a dark moon.
303 astronomical-dark hours in an average month
12.4 usable nights
10–13 in the middle half of years · 4.0 typically near a dark moon.
246 astronomical-dark hours in an average month
12.4 usable nights
9–15 in the middle half of years · 3.6 typically near a dark moon.
248 astronomical-dark hours in an average month
3.5 usable nights
2–5 in the middle half of years · 1.6 typically near a dark moon.
240 astronomical-dark hours in an average month
3.8 usable nights
2–5 in the middle half of years · 1.4 typically near a dark moon.
248 astronomical-dark hours in an average month
3.2 usable nights
2–5 in the middle half of years · 0.9 typically near a dark moon.
248 astronomical-dark hours in an average month
3.5 usable nights
1–6 in the middle half of years · 1.6 typically near a dark moon.
280 astronomical-dark hours in an average month
6.3 usable nights
3–10 in the middle half of years · 1.9 typically near a dark moon.
310 astronomical-dark hours in an average month
10.2 usable nights
7–14 in the middle half of years · 3.6 typically near a dark moon.
300 astronomical-dark hours in an average month
10.3 usable nights
7–14 in the middle half of years · 3.8 typically near a dark moon.
310 astronomical-dark hours in an average month
Use the baseline honestly
Climate chooses the month. Forecasts choose the night.
The cloud product is a roughly 1° regional grid. It can reveal seasonality, but it cannot know a mountain ridge, valley fog pocket, locked gate, smoke event or the exact sky you will get.
Source: NASA POWER daily data, parameter CLOUD_AMT_NIGHT from the CERES SYN1deg cloud product. GoodSeeing calculates astronomical darkness and lunar illumination independently for each place.