1.9 usable nights
1–2 in the middle half of years · 0.5 typically near a dark moon.
354 astronomical-dark hours in an average month
20-year trip-planning baseline
When to plan an observing trip to Norfolk County
August: 10.2 usable nights on average. A regional planning baseline, not a forecast for your trip.
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
August has been strongest.
It averages 10.2 usable nights, versus 0.5 in December. A typical August lands between 8 and 12 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
1.8 usable nights
1–3 in the middle half of years · 0.6 typically near a dark moon.
292 astronomical-dark hours in an average month
4.3 usable nights
2–6 in the middle half of years · 1.6 typically near a dark moon.
272 astronomical-dark hours in an average month
5.0 usable nights
3–7 in the middle half of years · 1.4 typically near a dark moon.
215 astronomical-dark hours in an average month
6.8 usable nights
5–9 in the middle half of years · 2.4 typically near a dark moon.
166 astronomical-dark hours in an average month
7.2 usable nights
5–9 in the middle half of years · 2.3 typically near a dark moon.
120 astronomical-dark hours in an average month
9.9 usable nights
8–12 in the middle half of years · 2.5 typically near a dark moon.
145 astronomical-dark hours in an average month
10.2 usable nights
8–12 in the middle half of years · 3.5 typically near a dark moon.
201 astronomical-dark hours in an average month
9.3 usable nights
7–12 in the middle half of years · 3.5 typically near a dark moon.
247 astronomical-dark hours in an average month
5.3 usable nights
4–6 in the middle half of years · 1.9 typically near a dark moon.
304 astronomical-dark hours in an average month
3.5 usable nights
2–5 in the middle half of years · 1.1 typically near a dark moon.
330 astronomical-dark hours in an average month
0.5 usable nights
0–0 in the middle half of years · 0.1 typically near a dark moon.
372 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.