Sydney's beaches will be buzzing over the next few days as lockdown-weary residents try to beat the heat of the city's warmest weekend in seven months.

Northwesterly winds developing ahead of an approaching cold front will cause temperatures to spike across NSW during the next 3-4 days.

Some areas are forecast to see daytime maximum temperatures climbing more than 10ºC above average between now and Monday.

Image: Forecast surface temperature at 1pm AEST on Saturday and Sunday afternoon, according to the ECMWF-HRES model.

This warm weather will be challenging for the state's Local Government Areas that remain in lockdown due to COVID-19.

With Sydney, Wollongong and the Central Coast still under stay-at-home orders this weekend, there will be restrictions on how many people can access the beaches as temperatures climb.

Sydney will see temperatures reaching around 28-29ºC on Saturday and Sunday, in both the city and western suburbs.

While Sydney's coastal fringe should be kept a little cooler by sea breezes, Bondi is still forecast to reach 25-26ºC on Saturday and Sunday.

Sydney's Observatory Hill weather station, the one next to the Harbour Bridge, hasn't had a weekend this warm since February. If both days get above 29.2ºC at the site, it will be the warmest weekend since January.

The early-spring warmth will also cause one of the season's first spikes in bush and grass fire danger in NSW, with Very High fire danger ratings likely in some parts of the state between Friday and Sunday.

Cooler weather will return to NSW from Sunday or Monday as a southwesterly change sweeps across the state.