Just to play around with the numbers a bit...

Google says that the drive from Fresno, CA to downtown Chicago is 2,209 miles long.  Let's assume that you're right, Umbra, and that a 1,638 mile truck trip carrying 38,000 pounds of produce emits 6,000 pounds of CO2.  Then a 2,209 mile trip emits about 8,000 pounds.  That's a little over a pound of CO2 for every 5 pounds of produce carted from the Central Valley to Chicago.

Using your freezer for 9 months emits 332 pounds of CO2.  I have no idea how much food you can pack in a freezer.  But I'd be surprised if it were more than a couple hundred pounds.  Let's be generous, and assume that we are freezing around 300 pounds of food.

Which means that shipping the veggies is...wait for it...about 5 times more carbon efficient than buying local and freezing.  

Now, obviously, there's lots of uncertainty here.  The actual trip can be longer (or shorter) than 2,209 miles.  Food grown in California & Illinois may use different amounts of fossil fuel inputs (fertilizer, tractor diesel, pesticides, seeds, etc.).  Cooking frozen foods can use more energy than fresh foods.  Refrigerator trucks may get worse mileage than regular diesel vehicles.  Ad nauseum.

But unless I'm mistaken, it looks like the numbers you present don't make much of a case for buying local.  Sadly enough.

What about eating naturally fermented foods during the winter?  All you need is an airtight glass or other container, fresh veggies or fruits, sometimes some salt and a little bit of time.  No freezer required!  And, it's a great way to get probiotics naturally!  

p.s. You can also turn to nature's greatest gift:  oxygen, and dry your foods, even meat if you eat it.

One last thing: Am I an idiot to think you may be able to buy from a local grower during the winter in Illinois? Some farm with a winter Community Supported Agriculture program? Ask around, on my idiotic behalf.

You might be...but depending on the method the farmer uses to grow crops during the winter (e.g., heated greenhouse), it might be less carbon intensive overall to get food shipped from elsewhere.