For now. And -20°F is not typical for a winter day in Iowa. There are cold snaps where it gets that low, but I don't believe it's the norm. I have family in northern Iowa, and I live it a colder part of the Midwest. -20°F basically doesn't happen at all for three quarters of the year, April through November. Even December -March it's still uncommon enough that it's usually thought of as a cold snap, and it's usually overnight. I don't think I have ever noticed a forecast in this part of the world with -20°F (or colder) listed as the day's high temperature.
It can get darn cold here. Cold enough to chase people like betarhoalphadelta. Last new years we had a really bad cold snap. But I think people who have lived here a while usually try not to road trip that much in winter, with the obvious exception of late December.
Road tripping at -20°F is, IMHO, getting into outlier territory.
I remember 2 days in the 22 years I lived in Chicago and then school at Purdue where we had days like that. -20F with -40 to -60 windchill. 2 days.
If you're making EV decisions based on something that happens 2 days out of 22 years, you might be overthinking it.
You know what else I remember about those two days? ICE vehicles were having trouble starting unless they were garaged, because of the viscosity of oil at those temps. We weren't far enough north where regular people needed engine block heaters. I remember the day in Chicago they shut down all the schools (I was in HS at the time) because the buses weren't starting.