2002 Intrepid engine light.

Hello I have a 2002 Intrepid ES, 2.7 liter engine with 84 K on it, I purchased it 6 months ago with 78 K, the car has been great until a couple days ago, it got fairly hot outside and the engine light came on but the car still ran and drove the same as it always did, fine. Now today its cool outside, I took the car out for a nice long drive, no engine light came on, so it would seem it only comes on in the hot weather.I stay on top of all the maintenance on the car but have not yet changed any sensors, but im reluctant to change a sensor, from what I read it may not be a sensor causing the problem at all and I do not want to spend a bunch of unnecessary cash. If someone could help steer me in the right direction I would so greatly appreciate it. Thank you in advance.