1. You don't have to work 

Which means you can continue sleeping in while listening to the sound of the rain. It is really my kind of simple pleasure. 

2. Chill weather makes perfect hot coffee

Or tea or milk or chocolate. Hot beverages taste more satisfying when drank on a rainy weather. 

3. Finally, a reason to to stay at home

And do whatever things that you have been postponing until now, e.g. house chores. Although if you are like me, you are pretty much gonna spending the rest of the day on the bed. Zzz.