Actually, I think that would help the humidity stay high.
Humidity also adds a few degrees to the temperature (holds it in).
You can get a radiant heat panel that you can mount somewhere, or a small space heater.
I use a space heater, they can get REALLY hot, so set it low to begin with and see how the temperature is after a few days before you set it higher.
Get a high quality one, it's worth paying extra for for something well made, for purposes of reducing the risk of fire and malfunction (overheating when set to low).