The weather is suitable outdoors for the activity you want to participate it. Sunny for a walk or a swim. Snowing for sking. Windy for sailing. If it's the weather you want outside then for you it's outdoorable.
"Oh look, it's outdoorable. Bring your coffee and let's sit in the sun."
"There's a good wind coming up, perfect for windsurfing. Yes finally it's outdoorable."
Me- I'm going to go get my favorite chair to sit on outside with you guys.
Them - what? you're favorite indoor chair? Won't it get ruined and dirty?
Me- No! It's OK, it's totally outdoorable.