Sydney's mild autumn is set to extend well into May even as cool overnight temperatures prompt residents to hunt for warmer doonas.

The city clocked its coolest April in nine years in terms of minimum temperatures as the skies largely cleared and rains mostly dried up, the Bureau of Meteorology said in its monthly report.

Observatory Hill had its driest April since 2010 and average sunshine levels were the most for the month since that year. Sydney Airport had almost an hour above average sunshine per day – at 7.8 hours – than is usual for April.

Minimum temperatures dropped just below average for the first April in 10 years, contrasting with record high overnight temperatures for March and Sydney's hottest ever summer in the preceding three months.