Ever stare at the sun? That's quite painful.
Now stare at the SL sun. Notice something?
Yup, totally NOT painful. You can stare at it as it traverses the SL skies and not one rod or cone in your retina will feel the hurt.
And there's never rain, either. Every day is, at most, partly cloudy.
The weather is always beautiful, the skies pure deep blue, the seas always calm and the tide is always in. It's perpetual summer, or if you're in the Snow sims it's perptual winter. The climate is always the same, never changes or experiences devasting storms or hurricanes. Doesn't even vary by the tiniest degree.
It's amusing that in a game where everything from buildings to people can change so rapidly, and yet still be so static.