Supercars drivers are likely to encounter hot weather and then rain this weekend at the Thrifty Newcastle 500.

Rain is a possibility on all three days of track action at what is the first race event for the Gen3 era, although highest on Sunday.

According to the Bureau of Meteorology, there is a five percent chance of rain on Friday, rising to 20 percent on Saturday and 70 percent on Sunday.

Possible rainfall for the latter is forecast at only zero to three millimetres, although there is a chance of a thunderstorm.

Drivers have already had an experience of their brand-new Gen3 race cars in the wet, given rain fell on and off at Sydney Motorsport Park when the official pre-season test was held last month.

Then, however, they were running on 2022-spec wet tyres rather than the new, softer compound which is available for the first time this weekend.

Furthermore, the rain never fell particularly hard that Wednesday at Eastern Creek, although it was enough for teams to undertake an important wet-weather systems check.

Competitors will also have an eye on the mercury during the weekend, with a maximum of 33 degrees Celsius predicted for Saturday.

Heat has been identified by Roland Dane as a key item to watch, for its effect on both cars and drivers, in his Speedcafe.com column this week.

The Repco Supercars Championship field has three, 45-minute practice sessions on Friday, then qualifying, a top 10 shootout, and a 95-lap/250km race on each of the Saturday and Sunday.

Weather forecast: Newcastle 500

Source: Bureau of Meteorology, as at Wednesday 8/3 at 04:45 AEDT