NEW Year's Eve crowds should prepare for temperatures up to the high-thirties with no sign of respite for the first week of 2020.

Severe to Extreme Heatwave conditions are already impacting areas of NSW, but we will see deteriorating conditions today and tomorrow with temperatures expected to increase significantly in some highly populated locations before the new year kicks in.

Tuesday's heat will see increased Fire Danger Ratings, with most areas currently forecast to reach Extreme, Severe or Very High levels.

Low-intensity to severe heatwave conditions are forecast through southwest Queensland to northeast NSW for Tuesday, Wednesday, Thursday and Friday.

So you had better stockup on those icy-poles, because temperatures are set to exceed 30C every day this week in parts of the Northern Rivers including Lismore, Byron Bay and Ballina, with minimum temperatures in the high teens to low 20s.

Lismore's average maximum temperature for December is 26.1C and 30.3C for January (2002-2019).

Towns further west including Casino will be a few degrees warmer with tempertures predicted to sit in the mid to high 30s all week - welcoming in the new year at 37C on Wednesday.

At 6am Monday 30 December, there were 100 bush and grass fires burning across NSW and 41 are not contained.

Ten areas are under Total Fire Bans with severe fire danger across the south of the state.

BOM has warned the air quality is likely to deteriorate on the east coast over the coming days.