[Wavytone]

Dunk the heat does not mean much seeing-wise, in winter the air is just as turbulent and there are thermals too.

What matters most ts the microclimate in your immediate vicinity - hot walls or cliffs facing west, or dark roofs that have soaked up the heat and over the evening release thermals under your line of sight.

Also bare fields or grassy paddocks with dark soils spell trouble - farmed paddocks or urban areas, the dark soil heats up and also holds a lot of moisture.

The best areas are those like the Katoomba airstrip - trees providing shade to keep the sun off the ground during the day, no hot buildings, cliffs or walls to create thermals under your line of sight, and pale sandy soil doesn't absorb much heat and releases it quickly, and also the sandy sandstone plateau doesn't hold much water so dew isn't an issue.

Conversely if observing from home in an urban area... The atmospheric turbulence will be bad if it has been a full-sun day, any tine of year...

FWIW flying the paraglider provides a very first-hand feeling of turbulence in the air, the force on the glider tips and the rough air is immediately felt in the control lines much the same as a soaring bird would feel in their tip feathers.

The other issue in winter is that humans gave this awkward tendency to heat their home at night, which causes really bad turbulence. Not good if trying to observe in suburbia !

There's another phenomenon too - laminar airflow vs turbulent airflow. At Hargraves or Mt Blackheath the west-facing cliffs hold quite a lot of heat and it takes hours for them to release it - as thermals - during the evening. While that might seem bad, the prevailing breeze is a westerly and thanks to the width of the valley the airflow is laminar - smooth, in other words - so warm riding air isn't really troublesome. As experienced in the paraglide, in the late evening the warm air rises very smoothly out of the valley and is free of turbulence. A very nice flight.

At the airstrip however it's another matter - being so far back (kilometers) from the western ridge means the breeze over the airfield is inevitably turbulent. Hopeless for paragliders and only tolerable with a prop and very big motor. And not ideal for telescopes.