Car "stalls" while driving in "hot and humid" weather with A/C on!

I have a 1993 ford taurus 3.8L V6 automatic GL. My problem is that my car will “stall” or “shut off” during “hot and humid” weather conditions. It “shut off” on me yesterday when it was 91 degrees. It will not do this during cooler temperatures of the fall and winter. Running the “air conditiong” while driving seems to make it “shut off” also. I thought the problem was the “ignition control module” but found that not to be the case. I no that using the “air conditioning” will make your car run hotter. With the “hot and humid” weather and the “air conditioning” running combined together is maybe overloading the engine and it will “shut off.” Can anybody tell me if they think this is correct and what can I do to solve my problem?

Do the overtemp light or the temp gauge work in this car? If so, is it running hot?