Sydney copped almost triple the usual rainfall in March and the sodden conditions are likely to extend well into April, the Bureau of Meteorology predicts.

The city collected 326.6 millimetres of rain for the month, the wettest March since 1975.

Few days had as much sunshine as the final day of the month. Before Friday, Sydney was on course to have its gloomiest March since 1989, with an average of just 4.3 hours of sunshine per day so far. A typical March has about 6.9 hours of sunshine a day.

If the parasol wasn't needed, the umbrella was. All but eight of the days had at least 0.2 millimetres of rain, the fewest number of dry March days in 27 years.