(Chiefly UK)

1. Healthy, feeling well.

2. Satisfactory, okay, a good outcome. Used to describe a situation that's been sorted out, or turned out okay.

May be derived from the fact that is rains so much in the UK that rain is just a normal fact of life.
1. "I see you're really sick with the flu. Please, get some rest, and I'll bring you some chicken soup. Soon, you'll be right as rain."

2. "She had lots of challenges in school. But, she studied really hard so by graduation everything was right as rain."
by AnglophileLady June 4, 2010
You can believe it to be true.
A common response to the comeback, "yeah, right."
Dad: Better watch it or I'm gonna make you come home early.

Kid: Yeah, right!

Dad: Right as rain, buddy.
by Tim Steffen July 19, 2005
something is just usual but you talk as if only you knew it.
Chris: If there is no change, this month is December.
Lisa: you talk right as rain!
by Phoebe is me January 3, 2017