When I lived west of Birmingham, AL, the biggest push of Baltimores was the last week of April. Therefore I think you're at least a couple weeks away from seeing them in Chicago, although a few could show up before that.

eBird data shows earliest reports over the past ten years have been toward the end of April.

When apple trees start to bloom the orioles show up in my yard. Guaranteed.

tj

Here in MA the orioles always show up within a day or two of the first hummingbird. If you follow the Spring 2013 Migration of Ruby-throated Hummingbirds map it might give you an idea of when to expect orioles.

Claire

I saw an orchard oriole yesterday in my backyard for the first time ever! So excited! lol!

I am thrilled!! I mean super excited!! I just spotted my first pair of Baltimore orioles today!! My neighbor has has an oriole feeder out for several years but we've never spotted one. Now she is in a nursing home and hasn't had anything in her feeder and NOW they showed up. So I rushed around my house and found some thick copper wire, wrapped it around a small plastic cup, glued a yellow lid to the bottom and filled it with home made oriole sugar water mixture. Crossing my fingers that they come back! I'm going to make another feeder with hooks to stick on some orange wedges. These are such stunning birds. How I spotted them was I was cleaning our sons bedroom and saw them out the window on the tops of my dogwood tree jumping across the tops. They did this for several minutes. I then rushed down to my yard after they flew off to see if they were in my yard but no luck. I sure hope they return. Absolutely STUNNING birds!!