"In the next few days we'll still see this heat and actually building heat through Wednesday and Thursday across the southern areas of NSW," Dr Melody Sturm of the Bureau of Meteorology said on Monday.

She said a high pressure system sitting over the Tasman See was providing largely sunny conditions, while a ridge over northern NSW was pulling down warm air from the north.

"We're seeing sunny conditions and warm air all in the same place and a lot of heat is being drawn to southern parts of the state, particularly the riverina and tablelands," Dr Sturm said.

She said Wagga Wagga was likely to see some of the highest temperatures in the state on Wednesday, but across the Far South Coast conditions were well above the January averages.

In both Cooma and Canberra, the forecast for Wednesday was eight degrees above the January average, with 36 and 33 forecast.

Dr Sturm said Wednesday would be the hottest day of the week along most of the coast, while the heatwave would continue into Thursday.

Eden and Merimbula are both expected to peak at 30 degrees on Wednesday with similar 26 to 28 degree tops on Thursday.

After reaching 33 on Monday, Bega will again reach 33 on Wednesday with 29 predicted for Thursday.

Further up the coast conditions are consistently hot across the board with Batemans Bay and Nowra forecast to tip over 32 degrees through Wednesday and Thursday.

Ulladulla is forecast to land just under 30 with peak temps of 29 predicted on Wednesday.

Dr Sturm said night time temperatures will provide little relief with nightly lows predicted to hover around 20 degrees for much of the coast.

However, she said a trough would push easing conditions late on Thursday or into Friday with day time highs to drop back to the low-to-mid 20s.