It has been a warm start to May in parts of northern WA, with Broome registering its warmest spell of days this late in the season for nearly 30 years.

A stagnant mass of warm air sitting over northwestern Australia has caused temperatures to climb more than five degrees above average during the last few days.

Monday ass Broome Airport's fourth consecutive day above 36 degrees, which hasn't happened this late in the season since 1990. It's also the equal second latest spell of days this warm, this late in the season on record, using data from the current airport and old post office observing sites. This join dataset stretches back to the late 1800s.

Broome is forecast to reach the mid-thirties until Wednesday, before cooling down by a few degrees during the second half of the week.