1994 Honda Accord high idle

When I first start my engine the idle performs normally. However, during summer ambient air temperatures as the engine gets warmer after running for awhile the idle speed increases to anywhere from 2000 to 3000 rpm. If I turn the car off and restart after 5 or 10 minutes after it has been ilding high it idles even higher until I've run it for a few minutes. THe engine then settles back to it's normal high idle of 2 to 3 thousand rpm. I do not have this problem during cooler times times of the year. Then it idles at it's normal engine speed of about 900 rpm. Can you tell me from this what sensor is bad?