When can you actually photograph the Milky Way?

Four conditions have to be true at the same time. Miss any one and you drive home with flat frames:

1. The galactic core is up. The photogenic core (around Sagittarius) sits at declination −29°, so from mid-northern latitudes it only clears the horizon well between roughly March and October, and the further north you are, the lower it stays. From 43°N it tops out near 18° altitude; above ~61°N it never rises usefully at all.
2. Astronomical darkness. The sun must be more than 18° below the horizon. In mid-summer at high latitudes this never happens — the "gray nights" problem — which is why June core season belongs to southern Europe.
3. Little or no moon. A moon above ~20% illumination washes the core out. Your usable nights cluster in the week around new moon, minus any hours when the moon is below the horizon anyway (a bright moon that has set doesn't count against you — this is exactly the kind of hour most people miss).
4. Cloud under ~25%. High thin cirrus can even add glow around stars, but anything more eats the shot. This is the condition that changes daily and makes fixed "Milky Way calendars" useless for planning a specific night.

The first three are pure astronomy — computable years ahead. The fourth is weather. ShootWindow multiplies them together hour by hour for your exact coordinates: core altitude and direction, sun depth, moon altitude and phase, and the hourly cloud forecast from the Norwegian Meteorological Institute. Hours scoring above threshold merge into windows like “Fri 22:40 → 02:10, peak 86/100 — Core 17° SSE · Moon down · Cloud 8%”.