outdoor electric

...  it safe to run an electric heating pad in an outdoor shed via an outdoor extension cord? I have been feeding and trying to tame a semi-feral cat on my property for about 6 months. The outdoor temperature is dipping down to near zero tonight. The cat sleeps in my outdoor shed. Even though I provided straw for the cat, I know cats can develop hypothermia easily. I used an outdoor extension cord to run electricity from my garage to the shed, and plugged in a drug-store type heating pad (set on low), and placed it in a cat bed with towells over it. Is this ...