1.1 usable nights
0–2 in the middle half of years · 0.2 typically near a dark moon.
357 astronomical-dark hours in an average month
20-year trip-planning baseline
Best time to stargaze at Walla Walla
July: 18.9 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.20.4–20.9 mag/arcsec²
The short answer
July has been strongest.
It averages 18.9 usable nights, versus 1.1 in January. A typical July lands between 16 and 21 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
3.3 usable nights
2–5 in the middle half of years · 1.1 typically near a dark moon.
292 astronomical-dark hours in an average month
3.4 usable nights
2–5 in the middle half of years · 0.8 typically near a dark moon.
267 astronomical-dark hours in an average month
4.7 usable nights
3–6 in the middle half of years · 1.8 typically near a dark moon.
202 astronomical-dark hours in an average month
7.0 usable nights
6–9 in the middle half of years · 2.5 typically near a dark moon.
141 astronomical-dark hours in an average month
2.7 usable nights
1–3 in the middle half of years · 1.0 typically near a dark moon.
79 astronomical-dark hours in an average month
18.9 usable nights
16–21 in the middle half of years · 6.5 typically near a dark moon.
119 astronomical-dark hours in an average month
16.4 usable nights
13–19 in the middle half of years · 6.0 typically near a dark moon.
183 astronomical-dark hours in an average month
12.7 usable nights
9–15 in the middle half of years · 3.8 typically near a dark moon.
244 astronomical-dark hours in an average month
7.5 usable nights
5–10 in the middle half of years · 2.0 typically near a dark moon.
303 astronomical-dark hours in an average month
3.0 usable nights
1–5 in the middle half of years · 0.8 typically near a dark moon.
334 astronomical-dark hours in an average month
1.9 usable nights
1–3 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.