How can I hang up one strand of Christmas lights outside with no available outlet?
It would be most safe to got with LED Christmas lights because they cannot catch on file and are low voltage. You can power them by a portable battery if you wanted or run an extension cord through the window or the wall.
They make solar christmas lights now. The first brand that comes to mind is Noma, available at Canadian Tire, but I'm sure other places have them as well. They charge during the day and automatically come on at night.
Eve P. is correct. An 14 awg out door cord would do just fine
You know, I was trying to find something to light up the ledge in my house and found a wireless outlet. It was at Walmart I think.