PARTS of NSW will experience a heatwave during the opening days of summer, setting the trend for the first month of the season.
A broad area of low pressure called a heat trough is funnelling hot air into the state from the north this week, while also triggering daily thunderstorms in some areas.
Temperatures have steadily risen in northern regions since the weekend and are likely to reach their peak during the opening days of summer.
Heatwave conditions are likely over the northern inland from Friday to Monday, when minimum and maximum temperatures will be about five to 10 degrees above average.
A number of centres should reach the low 40s on these four days, even pushing towards 43 or 44 at times in some areas.
Walgett could have its hottest December day in about seven years.
Southern and eastern districts will be spared from the early-season heatwave, although it won’t be a cool start to summer.
Wagga Wagga could reach 35 degrees on the weekend and Deniliquin is looking at a day in the high 30s.
The early-summer heatwave is the latest addition to an overall drying trend that has been occurring across NSW during the last two months.
This raises concerns about the remainder of the bushfire season in NSW.
Rainfall was near-to-below average across most of the state during October and November in response to a deteriorating negative Indian Ocean Dipole (IOD), a predominantly negative Southern Annular Mode (SAM) and unusually prevalent westerly winds.
These influences caused a remarkable and rapid turnaround from the record-breaking rain experienced during the middle of the year.
Summer is expected to be hotter and drier than usual, particularly in the opening weeks.
Both maximum and minimum temperatures are forecast to be above average and rainfall below average through in all areas during December.