9.4 usable nights
7–10 in the middle half of years · 3.3 typically near a dark moon.
341 astronomical-dark hours in an average month
20-year trip-planning baseline
Best time to stargaze at Sumter
October: 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.19.8–20.5 mag/arcsec²
The short answer
October has been strongest.
It averages 14.3 usable nights, versus 4.7 in July. A typical October lands between 11 and 18 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
7.8 usable nights
5–11 in the middle half of years · 2.4 typically near a dark moon.
287 astronomical-dark hours in an average month
9.2 usable nights
8–12 in the middle half of years · 3.1 typically near a dark moon.
288 astronomical-dark hours in an average month
9.7 usable nights
8–11 in the middle half of years · 3.6 typically near a dark moon.
240 astronomical-dark hours in an average month
9.0 usable nights
8–11 in the middle half of years · 2.6 typically near a dark moon.
207 astronomical-dark hours in an average month
6.2 usable nights
4–8 in the middle half of years · 1.9 typically near a dark moon.
180 astronomical-dark hours in an average month
4.7 usable nights
3–5 in the middle half of years · 1.3 typically near a dark moon.
192 astronomical-dark hours in an average month
6.4 usable nights
5–8 in the middle half of years · 2.4 typically near a dark moon.
242 astronomical-dark hours in an average month
10.8 usable nights
7–16 in the middle half of years · 3.4 typically near a dark moon.
257 astronomical-dark hours in an average month
14.3 usable nights
11–18 in the middle half of years · 5.0 typically near a dark moon.
310 astronomical-dark hours in an average month
11.8 usable nights
10–14 in the middle half of years · 3.4 typically near a dark moon.
326 astronomical-dark hours in an average month
8.7 usable nights
6–10 in the middle half of years · 2.8 typically near a dark moon.
354 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.