Yes, it has been 100+ degrees here in ChicagoLand for a few days. I walked into 
my house today, and it's not quite as cool as I think it should be.
I thought the A/C unit at this point just can't keep up. However the new A/C unit is only on its second season and it should be cooler.
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Off to the Internet I go...

Seems my programmable thermostat has batteries in it to keep it "talking" to my A/C unit.  A quick search on the 'net said most of them do. So I put some new batteries in and now all is cool! 
The bottom line is ... keep that thermostat "talking" to your A/C unit.