According to the weather service, the low temps in June should be 38 and July lows should be about 45. You will need some heat but how much you run it will determine your battery life. We set our furnace at 50 degrees overnight and throw on an extra quilt. The furnace only runs a couple of times every night. I recently purchased a Champion 2000i for topping off the battery every day. I should not have to run it very long.
I recently replaced my brand new WFCO converter with a Progressive Dynamics converter because the WFCO would not go into the 14.4 volt rapid charge mode, even when the battery was low to start. After reading about the failure rate of WFCO's, I decided not to bother with the warranty and with what I knew. I had a PD in my last RV and loved it, fast charging and low lost of battery water.