Nowra is set for top temperatures of 39, while Kiama and Ulladulla are expected to reach 32. 

Thankfully, a gusty southerly change is set to roll through in the afternoon, bringing temperatures down to the low 20s by Friday. The southerly is likely to result in a thunderstorm in the afternoon and early evening. 

According to the Bureau of Meteorology, a weakening high pressure system near New Zealand and a trough near the south east of the state are the cause of the impending storm. 

“The trough will shift towards the northeast today, bringing a somewhat cooler change to most southern and central districts,” it said. 

“The trough is expected to stall during Friday, decaying in coastal areas but lingering over the inland during the weekend as a new high shifts from the Bight to the Tasman Sea.” 

The Rural Fire Service has issued a very high danger for Thursday, with a total fire ban in effect. 

Meanwhile, Thursday’s predicted high temperatures have prompted the Australian Energy Market Operator to warn of potential power reserve shortages across NSW.

According to the BoM, a good proportion of thunderstorms develop when warm, humid air near the ground is forced upwards.

Thunderstorms can become severe when the atmosphere is particularly unstable and/or additional energy is drawn in from surrounding winds.