Help seriously overheating in warm weather

The IAT wouldn't cause anything like what you are describing. My only thoughts are perhapse a faulty thermostat? I used to work at a parts store for 4 years and have seen faulty brand new thermostats come back at least a few times a month. Did you try running the car since this occurred? If you did and it cooled properly, then that takes the thermostat out of the list of possibilities. Hope it didn't damage anything when it happened!

Same thing happened to me and turned out to be the temp sensor on the driver's side. Fixed it, $22.

I hear ya - I run a good bit hotter once we hit near 100 (it's 98* today). The stock radiator is paper thin - that's one issue. If you run hot till you hit the highway (or are at speed) but then cool down, the radiator is able to indeed reject enough heat. That would mean you run hot at low speeds. Check the fan wiring to make sure the connector isnt burning.

I agree with the cooling system tune-up ideas. A Mr Gasket t-stat (180 would be my choice) is leagues better than a parts store cheapo. Flushing the system is good - remember that water rejects heat 2.6 times better than EG antifreeze. Make sure the system is holding pressure (each PSI raises the boiling point about 3*F). Check and/or replace the cap if it is kinda old. Make sure the little plastic air dam is under the car.

Stuff like that can help. If you dont have a manual fan switch, it might be time to install one (for low speed at least).

Random thoughts. Good luck.

Good ideas. In my car, I have a 180 dg thermostat and new stock rad. Between that and the new fan and lower temp fan settings, I never go past 1/4 from the left on the temp guage in ANY heat. The stock fan settings let the car get too hot.

i has a similiar prob last year with mine. new radiator and thermaostat, ect sensor, fans coming on. everything was working but the car would still get hot especially in traffic or with ac. anyways, i finally re-replaced the thermy and i also replaced that little plastic air dam right under the front of the car because mine was broke off and i havent had any problems so far this summer, as a matter of fact the car hasnt went past the o yet. i have gotten bad replacement parts a few times(ect sensor more than once and thermy), especially from autozone.