Is that a morel?

Well, it appears that this is a historic day for Chicago in terms of a dry airmass. 61/7 comes out to a relative humidity of 11%. I went back through the records and I cannot find ANY day with 11% humidity in Chicago back into the 1940s, when reliable daily records for that began. Some data does exist back into the 1930s, but there are some gaps. There have been quite a few days with under 20% relative humidity and several days that got down to 12-13%, but not 11%.

These weather apps are smoking dope

Can officially record a trace for this winter

If you look at the visible satellite picture you would think there is one low pressure system but if you look at the water vapor loop it looks to be two (maybe three)