Here's why:

* Sunlight is necessary: Solar panels convert sunlight into electricity. Rain clouds block the sunlight from reaching the panels.

* Water and electricity don't mix: While solar panels are designed to be water-resistant, they aren't meant to be submerged. Direct contact with water can damage the panels and create a safety hazard.

However, there are some important things to keep in mind:

* Solar panels can still generate some power on cloudy days. Even when it's cloudy, there's still some sunlight reaching the earth. This can generate a small amount of power, although not as much as on a sunny day.

* Solar power systems often include batteries. This allows them to store energy generated during sunny days, which can be used when the sun is not shining, like on rainy days.

In summary, solar power relies on sunlight, and rain blocks this. However, solar systems can still provide power with the use of batteries.