4.1 usable nights
2–5 in the middle half of years · 1.4 typically near a dark moon.
354 astronomical-dark hours in an average month
20-year trip-planning baseline
Best time to stargaze at Boise
July: 19.3 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
Bright skyBortle classes describe observed sky conditions; this brightness model does not establish a measured Bortle class.18.9–19.6 mag/arcsec²
The short answer
July has been strongest.
It averages 19.3 usable nights, versus 3.9 in December. A typical July lands between 17 and 22 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
4.5 usable nights
2–7 in the middle half of years · 1.4 typically near a dark moon.
292 astronomical-dark hours in an average month
6.0 usable nights
4–8 in the middle half of years · 2.3 typically near a dark moon.
271 astronomical-dark hours in an average month
7.2 usable nights
4–8 in the middle half of years · 2.5 typically near a dark moon.
212 astronomical-dark hours in an average month
8.1 usable nights
5–11 in the middle half of years · 2.7 typically near a dark moon.
159 astronomical-dark hours in an average month
11.8 usable nights
9–14 in the middle half of years · 3.9 typically near a dark moon.
120 astronomical-dark hours in an average month
19.3 usable nights
17–22 in the middle half of years · 6.5 typically near a dark moon.
138 astronomical-dark hours in an average month
17.6 usable nights
16–20 in the middle half of years · 6.3 typically near a dark moon.
198 astronomical-dark hours in an average month
16.3 usable nights
14–18 in the middle half of years · 6.0 typically near a dark moon.
246 astronomical-dark hours in an average month
11.6 usable nights
9–15 in the middle half of years · 3.4 typically near a dark moon.
304 astronomical-dark hours in an average month
6.4 usable nights
3–10 in the middle half of years · 1.8 typically near a dark moon.
331 astronomical-dark hours in an average month
3.9 usable nights
1–5 in the middle half of years · 1.0 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.