I read a few threads on the subject and they seem to vary between "you'll be fine" and "your coop will burn down" so... I'm a bit confused. Can somebody more experienced please put my mind at ease? 
I live in a cold climate and will need a heated waterer for the winter, which means I'll need electricity in the coop. I was thinking of running a heavy duty outdoor extension cord from the garage to the coop, I think about 50 feet, and only have the water heater plugged into it (with a surge protector). Maybe also a small night light inside the coop, providing just enough light for me to collect eggs in the dark days of winter, but not bright enough to wake and bother the chickens. And no heating for the coop.
So, if I got this 60-watt thermostat-controlled waterer:
https://www.amazon.com/dp/B005BV1WLE/?tag=backy-20
And used this outdoor extension cord (either the 40ft or the 80ft, but not two linked together):
https://www.amazon.com/gp/product/B00004SQET/?tag=backy-20
would my life burn down? Outdoor electricity freaks me out, please help!

I live in a cold climate and will need a heated waterer for the winter, which means I'll need electricity in the coop. I was thinking of running a heavy duty outdoor extension cord from the garage to the coop, I think about 50 feet, and only have the water heater plugged into it (with a surge protector). Maybe also a small night light inside the coop, providing just enough light for me to collect eggs in the dark days of winter, but not bright enough to wake and bother the chickens. And no heating for the coop.
So, if I got this 60-watt thermostat-controlled waterer:
https://www.amazon.com/dp/B005BV1WLE/?tag=backy-20
And used this outdoor extension cord (either the 40ft or the 80ft, but not two linked together):
https://www.amazon.com/gp/product/B00004SQET/?tag=backy-20
would my life burn down? Outdoor electricity freaks me out, please help!