The climate varies with elevation. At Katoomba, (1,010 m or 3,314 ft) the summer average maximum temperature is around 22 °C with a few days extending into the 30s (80s–90s °F) although it is quite common to see maximum temperatures stay in the teens when east coast troughs persist.
Night-time temperatures are usually in the teens but can drop to single figures at times. During winter, the temperature is typically around 10 to 11 °C in the daytime with −1 °C or so on clear nights and 3 to 4 °C on cloudy nights. Very occasionally it will get down to -3C or slightly lower but usually the coldest air drains into the valleys during calm, clear nights.
The Blue Mountains is not known for particularly cold mornings compared to other areas on the Central Tablelands like Oberon, Bathurst and Orange etc. There are two to three snowfalls per year although settled snow has become less common in recent decades. In the lower mountains, however, the climate is significantly warmer.
Annual rainfall is about 1,050 millimetres (41 in) in the Upper Blue Mountains with many misty days.
Check the weather in the Blue Mountains. https://www.askroz.com.au/blog/weather-forecast