99 Metro engine runs Cold-Warm-Cold-warm

Metro does the darndest thing engine temp gauge swings slowly to warm then slowly to cold and back to warm again every 15 minutes or so.
The passenger compartment heater cannot defog the winshield with out the help of a towel even after two hours of driving. It seems the heater cycles with the engine temp gauge. Oh it never gets remotly warm in the car.
KT

It rains a lot here in the Gig harbor, Seattle area. I had thought the vent system would just draw in more moisture.
I Suspect low engine water level was part of my problem, found a leaky heater hose. Will keep an eye on water for the next few days to be sure.

KT