September is least crowded for us. But we PREFER very early February before Pres. day crowds. Perfect weather in Feb.
But our all time least crowded and possibly best ever day was the day after a tropical storm in Sept. That morning it was still pouring, so we did a VERY crowded character breakfast in the hotel. As everyone else went back to the room, we pulled on panchos and headed to the AK - animals LOVE rain. A half mile before the parking lot, the rain stopped and turned to a very light, cool mist. We stayed for about 4 or 5 hours. The safari vehicles had to stop to let animals get out of the road several times. The tigers at the ruins were jumping and playing like a 500lb version of our house cat. When we left, they had only used 5 rows of parking for the entire day - that's 5 single rows, or 2 1/2 of the double parked rows. There were a hundred times as many cars in the cast member parking.
Down Side - the rest of the September trip was normal low crowds (not extremely low) with MUCH HIGHER THAN NORMAL HUMIDITY.
We might be going the 1st week in Feb this year depending on what my pregnant DW feels like doing.