I had a bad head gasket on an old civic in college. The temp started reading high, but always cooled down on straight-away driving, since more air was passing over the radiator. Went back up when I stopped. Since I was so poor, I turned the heater on full-blast all year long to keep it running (the summers were heck!).

If it's not electrical, and you temp really matches the gauge, consider a bad head-gasket (as I recall, the color of your exhaust may change as well, since radiator fluid is getting above the pistons). Someone can chime in, but you might also consider a bad water pump or clogged up radiator.

William
98 Civic + 03 Pilot