It looks like flurries maybe between 8 and 10 pm, and snow showers after 10 til early morning. It’s saying only 3-5 inches over night. That’s not much in Ohio, so I imagine this is negligible in Iowa.
And it’s not really that cold, in the 30’s, so I don’t see this weather keeping anyone from attending. If it were actually heavily snowing, even then Iowans should be comfortable with that, except maybe older people. I would expect older people to be Cruz supporters if evangelicals and establishment types if not.
Wait a minute, I am an older person and I am for Trump and will crawl to the polls if necessary. :-)