Is a leaking roof an emergency?
A leak becomes urgent when significant water is entering the property, ceilings are bulging or sagging, roofing materials are unsafe, or water is close to electrical fittings. Smaller leaks may not require an out-of-hours callout, but they should still be investigated promptly because continued water ingress can cause wider damage.
Judging urgency
Not every leak needs an immediate call-out, but some do. Water running rather than dripping, water near light fittings or consumer units, a ceiling that is bulging or sagging, and leaks during ongoing severe weather all justify treating the situation as urgent.
A slow stain that appears only in prolonged rain is usually a scheduled repair rather than an emergency, though it still needs dealing with before it grows.
What to do while you wait
Move belongings clear, put a container under the drip and, if a ceiling is holding water, keep people out of the room. If water is anywhere near electrics, isolate the circuit and treat it as a safety issue first.
Do not climb onto a wet roof or work at height in wind to try to contain it. Temporary protection from outside is a job for someone equipped to do it safely.