Flickering covers everything from a cheap LED bulb to a service-level fault that will eventually damage your appliances. Sorting them out is mostly a matter of asking where and when.
One fixture flickers
Least worrying. Usually a loose bulb, a worn socket, or an LED paired with a dimmer it was never designed for. Swap the bulb first; if it persists with a known-good bulb, the fixture or its switch is the suspect.
One room flickers
Points at a shared connection on that circuit — often a back-stabbed receptacle where the circuit passes through on its way to everything downstream. Common, cheap to fix, and worth fixing because a loose connection makes heat.
The whole house flickers
This is the one to take seriously. Whole-house flickering, especially with lights that brighten as well as dim, points at a loose or failing neutral at the service. Under that condition the voltage on your two legs stops balancing, and electronics on the high leg can be damaged. Call an emergency electrician rather than waiting.
Flickers when the AC or fridge starts
A brief dip on motor start is normal physics. What is not normal is a deep, sustained dip, or one that has clearly got worse over months. That pattern suggests undersized service or a deteriorating connection, and often ends in an electrical panel upgrade.
Flickers after rain or wind
Look up. Weather-linked flickering frequently traces to the service drop, weatherhead or mast, particularly if a tree limb is anywhere near the line. That may be utility-side, but everything from the weatherhead in is yours.
What to check before you call
- Does it happen with a different bulb?
- Is it one fixture, one room, or everything?
- Does it correlate with a specific appliance starting?
- Do any switch plates or outlets feel warm?
- Are your neighbours seeing the same thing?
That answer set gets a good electrician most of the way to a diagnosis before arriving. See electrical repair & troubleshooting for what a troubleshooting visit involves, or lighting installation if the real answer is that the fixtures themselves are done.