Outdoor kitchens are great for entertaining! Check out our recent blog on how to create the perfect outdoor bar area. It includes counter top suggestions for the outdoors!

http://granitegrannies.com/design-tips-how-to-create-the-perfect-outdoor-bar/

If you don't mind some maintenance, this mahogany top is coming out great:

I guess it kind of depends on what material you're building the outdoor kitchen with. Stone veneer? brick? We're not in the Chicago area but the Pacific Northwest, but have done quite a few outdoor kitchens and we like to lean towards granite also. It becomes such a beautiful compliment and durable feature to your outdoor kitchen. There's also other materials stone slabs, brick, slate...etc.

As landscape architects and contractors in the Chicago area, we have designed and built several outdoor kitchens. We recommend going with a solid slab countertop here in this climate. Exposed grout on horizontal surfaces - as with tile, is not recommended. We have done bluestone, polished granite and honed granite (matte) countertops. See below examples.

@elaineday, if you are still considering options for countertops, might I suggest concrete. I've attached a few pics of one I built 4 years ago in SW Wisconsin and it looks even better today than when first placed. No issues with cracking, fading, or wear. There are some additional pics on my profile page. Feel free to check them out, and if you have any further questions regarding concrete,, feel free to ask and I'd be glad to answer.

Echoing some of what's already said, natural or man-made slabs and cast-concrete will all serve you well and look great.
Good luck!

Caesarstone all the way!

Caesarstone or any other manmade quartz product are NOT suitable for outside. Warranties are void if product is outdoors. Only natural stone, in any shape and finish, preferably granite, slate, soapstone.