3.3 usable nights
1–4 in the middle half of years · 0.6 typically near a dark moon.
355 astronomical-dark hours in an average month
20-year trip-planning baseline
Best time to stargaze at Eugene
July: 20.4 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
Bright skyBortle classes describe observed sky conditions; this brightness model does not establish a measured Bortle class.19.2–19.9 mag/arcsec²
The short answer
July has been strongest.
It averages 20.4 usable nights, versus 2.8 in February. A typical July lands between 18 and 24 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
2.8 usable nights
1–4 in the middle half of years · 0.7 typically near a dark moon.
292 astronomical-dark hours in an average month
3.1 usable nights
1–5 in the middle half of years · 1.1 typically near a dark moon.
270 astronomical-dark hours in an average month
3.8 usable nights
1–6 in the middle half of years · 1.4 typically near a dark moon.
210 astronomical-dark hours in an average month
7.3 usable nights
4–11 in the middle half of years · 3.0 typically near a dark moon.
156 astronomical-dark hours in an average month
9.1 usable nights
6–11 in the middle half of years · 3.1 typically near a dark moon.
120 astronomical-dark hours in an average month
20.4 usable nights
18–24 in the middle half of years · 7.0 typically near a dark moon.
134 astronomical-dark hours in an average month
18.6 usable nights
16–21 in the middle half of years · 7.3 typically near a dark moon.
196 astronomical-dark hours in an average month
13.3 usable nights
12–14 in the middle half of years · 4.8 typically near a dark moon.
246 astronomical-dark hours in an average month
8.9 usable nights
5–12 in the middle half of years · 2.2 typically near a dark moon.
304 astronomical-dark hours in an average month
3.6 usable nights
1–6 in the middle half of years · 0.8 typically near a dark moon.
332 astronomical-dark hours in an average month
3.1 usable nights
1–5 in the middle half of years · 0.6 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.