What is a storm?

When in England, I always thought a storm involved something dramatic. Like a Thunderstorm with its noise and lightning. Or a dumping of snow.

In Canada I read of a pending snowstorm and I picture a blizzard but it could be just a couple of inches of snow.

Today there's another storm predicted. I first heard it on the radio and that station often overstates what we really get. But on the weather network there's actually a storm warning. Yet the forecast for each part of the day - afternoon, evening, overnight, morning - just says light rain.

Hard to think of light rain, even if continuous, as a storm.