Sydney, and most of the rest of NSW, has posted a relatively hot start to the year, with the unseasonable warmth set to extend well into April. Those hoping for more rain will also have to wait.

Maximum temperatures at Sydney's Observatory Hill were a full 2 degrees above the March average last month. The 38.4-degree reading on March 18 was also the city's warmest this late in the season since 1940, the Bureau of Meteorology said.

For the first three months of the year, NSW's daytime temperatures were 2.65 degrees above the 1961-90 norm, making it the second hottest beginning to any year, Blair Trewin, the bureau's senior climatologist said. Only January-March last year was warmer.

Sydney's long, hot summer has a way to go before the autumn chill arrives. Credit:Christopher Pearce

This month has started on a warm note too. Sunday was the state's fourth-warmest April day on record, based on area averages, Dr Trewin said.