If I let the car warm up for 10 minutes with the heater set on any level it blows warm air not hot. replaced thermostat. I'm worried when it really gets cold in Chicago is it going to be enough to heat the car? what should I check
You should check your coolant system. One possible problem is that the coolant hasn't been changed, and so it's gotten gunked up and clogged the heater core. It's not easy to verify this directly, but (when the engine is cold!) unscrew the radiator cap (or expansion tank cap) and take a look at the coolant. If it looks brown/muddy, it could indicate that dirt is clogging parts of the system.
This is most likely the cause of the problem (unless there's been some major trauma to the car). If so, you can try a coolant flush. You'll want to look up the exact procedure for your car, but briefly, it involves finding the drain plug at the bottom of the radiator and opening it to empty the coolant in the radiator. Please collect this and dispose of it at a recycling facility. Antifreeze is toxic and many recycling centers will take it for free.
Continuing on, your vehicle should be tall enough to do this without jacks. If you feel adventurous, you can even remove the engine drain plug (for coolant, not oil). Once both are drained and the plugs reinstalled (check if you need new O-rings or crush washers), you can refill the system with a bottle of radiator flush, which you can find at an auto parts store, and an appropriate amount of distilled or deionized water. Both are easily found, but don't use straight tap water, since the ions in the water can cause corrosion. Check your owner's manual for the amount of water required. Be sure to follow the directions on the radiator flush bottle as well. This will generally include driving for a bit with the heat on.
Next, you'll drain the system again, and refill with a 50/50 mixture of antifreeze and distilled/deionized water. Your owner's manual should specify what type of antifreeze to get.
Don't attempt this if it is already below freezing, since there's a possibility that the radiator flush won't prevent the water from freezing, which would be bad.
If it turns out that this isn't likely the issue (coolant looks good, or flush didn't work), then there may be other issues present, such as: 1) Broken heater core valves 2) Air bubble trapped in coolant line to heater core 3) Broken blend door
All of those are somewhat harder to resolve than a simple radiator flush, but DIY instructions can be pretty quickly found online. There's even a forum for your car.
Hopefully this helps you diagnose the problem!