More is more in this case. Depending on the size of the skylight, I would opt for the stronger unit. You could also use a dome shaped unit to shed the snow or rip the curbing down so that the skylight sits at and angle to the roof.

It's a small skylight at the top of a stairwell. It measures 41 x 41. I don't see that the Velux comes in a dome shape unless I go to the polycarbonate type.

What is the next most standard size? Sometimes you can go up or down a tiny bit and just change some of the curb framing for the adjustment.

All domes will be poly-carbonate as far as I am aware.

I am a little confused now. I had wanted to get away from the plexiglass dome. The old one I have now is that, and there is no UV protection or insulation. The Velux I am looking at is UV protected with 2 layers of glass with argon between them. Are you saying I should get a dome style instead, regardless that they only come in plexiglass?

Will do Millworkman!

Here in Milwaukee (same weather) I don't know that I have ever sold a snow load unit, or even gotten that recommendation. Perhaps it is the flat roof that they are concerned about. Definitely does not hurt to get it though.

I will see what the upcharge is for the snowload option, and if it's not way high, I'll get it, just so I don't have to worry about it or think about it at the next blizzard. Like you said, the roof is flat. I can't imagine that snowload strength would be really a lot more money, since the skylight won't be big.