Spring is in the air, but has the cold weather disappeared?
BALMY nights and the hint of rain - it sounds like a delightful spring is in store for Northern Rivers residents, but we might still have a few cold nights ahead of us before winter is done.
The Bureau of Meteorology said parts of NSW will experience windy, cold conditions later this week, with temperatures over the weekend dropping by as much as 4-8 degrees below average and wind speeds reaching up to 35km/h.
Significant snowfall is expected across the Alps this week and is also forecast to fall at low levels along the NSW ranges on the weekend, including parts of the Central Tablelands, Southern Tablelands, Northern Tablelands and higher parts of the ACT.
By Thursday, temperatures in Lismore will drop to by up to five degrees, with daytime temperatures of 19C on Monday, falling to a minimum of 3C overnight.
Daytime temperatures in Casino will remain in the low 20s, with minimum overnight temperatures of 3C on Monday.
Ballina temperatures will only reach a maximum of 18C and minimum of 6C on Monday.
Temperatures will be a little warmer in Byron Bay, dropping to 17C maximum and 10C minimum on Monday.
In longer range forecasts, BoM said above average rainfall was expected across much of the country, including the Northern Rivers, from September to November.
Little rainfall was expected to fall on the Northern Rivers over the next eight days and it may be September before decent widespread rain falls.
Cooler than average days are likely across much of NSW and southern Queensland in spring, but the nights are expected to be warmer than average.
BoM raised its El Nino-Southern Oscillation Outlook to La Nina ALERT status, meaning the chance of a La Nina occurring this year has increased to 70 per cent, roughly three times the normal likelihood.
BoM's manager of Climate Operations, Dr Andrew Watkins, said La Nina typically results in above-average winter-spring rainfall for Australia, particularly across eastern, central and northern regions.
"It typically also brings cooler and cloudier days, more tropical cyclones, and an earlier onset of the first rains of the wet season across the north," Dr Watkins said.
"The cooling of surface temperatures in the tropical Pacific Ocean and an increase in the strength of the Pacific Trade Winds indicates the chance of La Nina has risen. When these two changes occur at the same time, at this time of year, we see a greatly increased chance of a La Nina forming and persisting through spring.
"Climate models suggest that further ocean cooling and intensification of Trade Winds may occur over the coming months, which has triggered the bureau to shift from a La Nina Watch, issued on June 26, to a La Nina Alert."
The last significant La Nina event was in 2010-11, which was the Australia's wettest two-year period on record beating the previous record from the La Nina years of 1973-74. The last time the Pacific Ocean approached La Nina conditions was in late 2017, but thresholds were only briefly exceeded.
BoM will continue monitoring the situation closely.