What is that sound?

So this morning, getting ready for work (kind of) I was scrolling through the muted TV channels looking for some coverage of the 'lympics when I heard the strangest noise. After ruling out the wind (there wasn't any breeze), the A/C hadn't kicked in and it wasn't the train going passed...I was stumped. I called out to Josie "What is that noise?"

"It's rain dear..."

Oh. Wow, I guess it's been a while!