Crazy day in the Spark EV

Ok I hope someone can help me out on this one. I jumped in the car to run up town yesterday it was a bout 22 degrees outside,, So it was cold. The car had about 30 miles on it so I decided that would be enough. I turned on the seat heater and the heater. About half way there I noticed it had dropped to 25 miles so I turned off the heat. I kept going then all of a sudden noticed the range was climbing it was now up to 27 and kept climbing. I also noticed the battery gauge was climbing. By the time I got to Home Depot it said I had 60 miles,, I left with 30.. In the summer it may get 78 miles but only about 45 to 53 in the winter. I came back out from Home Depot and it had 32 miles by the time I got home it was around 50 miles... Has anyone ever had this issue..I was worried this thing was going to explode.. I plugged it in and will check it later today to see what charge it took.