Sydneysiders, and much of the east coast, might want to keep their raincoats and umbrellas handy over the next week.

A low pressure trough extending down from the north will combine with a very moist onshore flow to bring widespread heavy rain to much of the east coast.

Sydney's average monthly rainfall for February is just shy of 118mm, a total it has only exceeded three times in the last 10 years (239.mm in 2010, 165.4mm in 2013 and 205.2mm in 2017).

Due to the combination of the trough and moisture from the east, this year is also likely to at least reach the average rainfall for the month. Friday to Monday is the standout period when around 100-200mm could fall over the city, which would comfortably bring Sydney's monthly total above the average in just four days.

With over half the month to go and further rainfall a good chance, it is not unrealistic that the city could have received over 300mm by the end of the month.

Should the city's rain gauge record more than 300mm this month it would be the wettest month since March 2017 when 326.6mm was recorded. It would also be only the 6th time 300mm has been exceeded in any month since June 2007 when 510.6mm was recorded, with June 2013 (316.4mm), April 2015 (366.8mm), June 2016 (305.0mm) and March 2017 (326.6mm) the other instances.