Fire crews battling more than 50 bushfires across NSW are racing to strengthen containment lines, with searing heat and gusty winds expected to prompt severe fire danger across the state this week.

There are 62 fires burning across NSW, 35 of which have not been contained, as of 5pm on Sunday.

Seven 'watch and act' alerts are in place for residents, including for the Gospers Mountain fire that has scorched 119,000 hectares of bushland and threatened homes in the Hawkesbury area north-west of Sydney over the weekend.

Sydney experienced milder weather conditions on Sunday, with cloudy skies and light rains in some coastal areas. But severe fire danger conditions remain in the state's north with total fire bans in place for the Far North Coast, New England, Northern Slopes, North Western and Greater Hunter.