UK Lionel
Hello & Wellcome to the Forum!

Lionel, Outdoors?  Absolutely.
O scale outdoors is quite common in Great  Britan.
I have acquaintences that run 32 mm GarGraves stainless track indoors & outdoors for their mechanical & electric O scale trains.  Gargraves uses UV resistant plastic for its' track ties making them stable outdoors.
There are other manufacturers, but regardless of brand, having UV resistant ties and solid rail are what is important.

Slowly I am remanufacturing  G scale track(48" diameter curves & straights) into 32 mm(2 rail) for my mechanical trains to be used outdoors.

Happy Rails!
dave

Tho not O scale, G Scale Central - gscalecentral.net  is a british forum/group that you can check out and meet folks near you who are playing with their trains, outdoors.