During cold weather I have the same problem. I fill my tanks back up with the water hose and it comes out very cold. My 156 gallon tank will require two buckets of hot water and my 265 takes four buckets of hot water to keep the temp around 80 degrees. Just make sure you don't just dump in all the hot water at once. I let the tank fill up a little, add half a bucket, fill some more, add hot water and keep doing that until full. That way the water stays right around 80 the whole time.
In the summer around July and August, the water comes out of the hose about 83-84 and is a little too warm lol but that's ok, never had a problem.