The only problem is that extension cords are not made to be outside in the elements. Now as an electrician I'd say wire up a receptacle out there, but as a friend on this site, id say
Grab some 1" electrical pvc for cheap money.(double check that the extension cord end will fit in there) Electrical PVC comes with couplings built in on the ends.
Grab some pvc glue.
Piece them together to what ever length you need.
Now if you have a metal snake, great, throw that sucker in there. If you dont, get some decent string or small light rope.
Tie 1 or two shopping bags or even trash bags on there so it kind of looks like a football penalty marker.
The bag is just acting like a seal with little friction. So adjust accordingly
Next grab the shop vac and suck on the other end just check on the pipe frequently to see if you have the string.
Use the string to tie to the extension cord and pull it through!
Tape the ends of the PVC with gorilla tape or duct tape
And that's how to hack it in there. lol.
i would NEVER do that at work. But member to member, it will work MUCH better than just leaving it on the ground.
Ohh and make sure your GFCI receptacle is working properly.