A five-week old kitten has survived after being left stuffed in a small letterbox on a scorching hot day in Wellington.

Susan McNair runs the Kitten Inn in Kelson, in Lower Hutt where she takes in stray kittens and re-homes them.

"It was stuffed in there, little face pressed up against the slot, obviously trying to get more air. After I took it out of the letterbox it just collapsed in my hands."

Susan McNair says kittens regularly turn up in suitcases, boxes, crates, bags and even in the leather-jacket of a big burly bikey guy, but never has one been left in her letterbox.

"Surprisingly she is doing just fine. She was a bit shellshocked yesterday, but now she's curled up in a little ball in my lounge."

Ms McNair says she always leaves a cage by her door for people to put kittens in, so using the letterbox is totally unnecessary.