I just posted a note on "basements are they here to stay",in that thread i noted that i have my layout (HO) outdoors. Yes it is in my back yard for almost a year and i have not experienced any distorsion,or warpage.I
just went thru a blizzard with 18" of snow,after sweeping off the snow, the track was still intact. The most i do is to put a tarp over it when not in use.
Normally i leave all my equipement under wraps(power pack,rolling stock,and locos) but with the temperature going dowm to 8 degrees f., just the locos were brought inside.I have never
enjoyed my hobby as i do now.