Wintry air descended across the southeast in the early hours of Sunday morning, bringing sub-zero temperatures to parts of the ACT and NSW, including Canberra.

Just after 6:30am, the nation's capital dropped to –0.1ºC, which was not only its coldest temperature since October 2023, but also its first sub-zero temperature of 2024. Frost warnings were also in place across Victoria's Wimmera and South Australia's Upper South East. 

Images: Observed temperature readings (top) and wind speeds (bottom) at 6:45am AEST (6:15am ACST) on Sunday, April 21st. 

Skies cleared and winds stood near-stationary under a strong high pressure ridge, allowing surface warmth to radiate upwards, well into the atmosphere. 

Figure: A broad high pressure cell extending across the southeast, centred over SA's Upper South East on Sunday morning.

Not far from the capital, Cooma Airport in NSW dropped to –3.6ºC after 5am, making it the coldest April temperature since 2021 and the coldest temperature in any month since October 2023.

Elsewhere, a number of locations recorded their coldest April mornings in years, including:  

• Deniliquin Airport (NSW): 1.8ºC, lowest since 2012 
• Cape Borda (SA): 6.6ºC, lowest since 2008 
• Adelaide Airport (SA): 5.4ºC, lowest since 2002 
• Edithburgh (SA): 3.8ºC, lowest since 2000 
• Ceduna (SA): 0.9ºC, lowest since 1999 

Whilst high pressure and clearer skies can bring cold mornings, they can also bring warmer days. On Monday, several of these very same locations are expected to exceed monthly averages. 

• Ceduna (SA): 28ºC (about 4ºC above average) 
• Canberra (ACT): 23ºC (about 2ºC above average) 
• Adelaide (SA): 24ºC (about 1ºC above average) 

To know when you can expect the next bouts of cold, hot, wet and dry weather, keep up to date with the latest forecasts here and check the latest warnings here.