Yeah it's still fine for sure. September holds plenty of great climbing weather. Obviously it continues to get colder and the days get shorter the longer you wait. But even through October I've climbed up there without cold weather or snow/ice gear.
Exact temperature obviously fluctuates greatly depending on weather and immediate geography. But in general, right now it will drop below freezing at high altitudes (12k or so). Below overnight lows will likely be 30s and 40s.