Commuting is likely to be a damp affair on Wednesday morning, after steady showers settled over Sydney on Tuesday.

Parts of the city's west including Baulkham Hills, Prospect and Blacktown copped more than 50mm from 9am to 6pm, causing flash flooding, while Mt Boyce in the Blue Mountains was drenched with 72mm of rain in the same period.

The Bureau of Meteorology is predicting rain and thunderstorms to linger in Sydney for the rest of the week. Up to 15mm of rain is expected in the city on Wednesday, with conditions expected to improve throughout the day.

Thunderstorms threatened the city on Tuesday morning, with heavy falls earlier in the day over an arc stretching from Gosford in the north around to Blacktown and Penrith in Sydney's west.