Suggest you also post on the Rocky Mountains forum - and the Canadian one. The RMF is very active and there are bound to be posters there with experience - eg Coloradans. Is horticultural fleece an option? The thicker versions, of course...

I'm in similar circumstances in PA, but luckily just with lettuce and cole crops. Happens to me every year. My plants are small, so I have them covered with milk jugs cloches. Tomorrow, I will run Christmas lights (small worked last year, trying the large ones this year) between the plants, then cover everything with a frost tarp (canvas painters tarp). The lights definitely increase the temperature under the tarp. I don't know if it will be enough to save tomatoes, but it is worth a try. I posted recently with a picture of my plant-tent city. I've included a link below. Let us know if you are able to save them! Good luck tomorrow, Bellatrix Here is a link that might be useful: Frost Cover Tent with Christmas Lights picture

Glass beats plastic for the simple reason that it is far denser for the amount of light let in. But yes, the plastic would be easier. You could use floating row cover to add insulation. Drape it over your cage, then drape the plastic over. This will add 4-6 degrees of frost protection, depending on how much of the base is covered - the more of a triangular shape you achieve, the better.

From Margret Roach at the blog "A Way to Garden." I'd rather turn large containers and boxes (or my carts) upside-down over things than lay material right on top of succulent, tender plants especially when high winds are forecast that will whip the material around. Steve Here is a link that might be useful: Coping with Spring Frost in a Garden