I can't figure out why one should get icing when there is a 20 degree spread between temp and dewpoint, no clouds, and the windscreen and airframe starts icing up, forcing a switch away from Live weather. I think I will only fly in areas where the temp is well above freezing. 

The icing effect on aircraft is massively overtuned in MSFS right now.  They've acknowledged it and said it'll be worked on, and they are also going to introduce toggles to let you turn it off if you want.