Why do my lights flicker?

Start with the boring causes, which cover most cases. A bulb not screwed in fully flickers, as does an LED bulb paired with an older dimmer built for incandescent loads, one of the most common complaints after a lighting upgrade and fixed by installing an LED-compatible dimmer or a dimmable bulb rated for it. Momentary dimming when the air conditioner, dryer, or well pump kicks on is normal inrush current, annoying but expected. Loose bulbs in a fixture whose socket contact has flattened over time also flicker and are worth checking.

The version that is not benign is flickering across multiple rooms or circuits, flickering that worsens over time, or flickering alongside warm or discolored outlets and switch plates, a buzzing sound, or any burning smell. Those point to loose connections, an overloaded or failing circuit, deteriorating wiring, or a problem at the main panel or service connection, and loose connections generate heat, which is a genuine fire risk. That is an electrician call, not a DIY project. If the whole house dims and brightens, notify the utility as well, since it can indicate a failing neutral on the service side, which damages appliances and needs urgent attention.