I have the same card. It has what's called a spin-up bug, keeping the fan at 0% until it hits like 85C, then going to 100% for a while to get it back down to around 70C, then repeats the process. The fan is supposed to have a more efficient PWM feature to control noise / cooling performance, but it sucks at it.
I use Rivatuner to have the fan set at 60% at all times, whether gaming or not. This keeps my GPU at around 45C idle and 65C load, and it's rather quiet at that level.
Keep that fan blowing air onto it, it will help keep it even cooler. You may be able to keep the fan at like 30 or 40% at idle, and have Rivatuner speed it up to 60% during gaming, and it should keep it plenty cool enough.