I would use sand bags to hold the plastic down.

Milk jugs or clorox jugs filled with water make quick, easy weights, too.

Sand bags and jugs of water will hold down the bottom edge of the plastic. But if you are trying to tape plastic at the corners, I found that spring clothes pins work for me. The silver tape came right off. I had to cover a large shade house for my orchid collection. I have several overturned garbage cans with a big rock on each to hold my tarps from billowing in the wind. We are in the middle of 10 days in a row with temperatures below 70 degrees. And Saturday is going to be bone-chilling under 50 degrees and rainy.
Linda Leaf

What about velcro?

thanks for your thoughts and ideas...
on short notice I can't get the water bottles or sandbags in place but will try to improvise where I can.
I don't have enough extra plastic to use the clothes pins.
I tried velcro...the sticky kind...and it doesn't stick in the cold...grrr

Next year...more planning!