It's been a wet month for Sydney, but just how wet, and how does it affect the cities annual rainfall?

With just over 108mm of rainfall, this October comes in well above the average of 76.6mm Whilst it is significantly more than October 2019 which received less than half the monthly average at 35.4mm, it is comfortably beaten by October 2018 with near 170mm.

Of the last decade, October 2020 comes in at second wettest behind 2018. It is also the fourth wettest of the last 20 years, and fifth wettest of the last 30 years.

Himawari-8 Infrared satellite with radar and lightning overlay showing heavy rain over Sydney to start November

This month's rainfall gives a healthy boost to the city's annual rainfall, adding to what was already more than the average annual rainfall expected to fall on the harbour city. With this month's additional rainfall, Sydney has already received more rainfall than 2019, 2018 or 2017. In fact, rainfall in Sydney is already more than the annual rainfall of all but two years in the last decade.

Sydney's current annual rainfall stands at 1363.6mm, with only the annual rainfall of 2016 (1385.6mm) and 2011 (1369.2mm) topping this in the last decade. With models picking around 15-20mm of rainfall in the first week of November, the 2011 total will shortly be surpassed, with the 2016 total likely being beaten not long after.

Should 2016's annual rainfall be topped, it would be Sydney's wettest year since 2007, when 1499.2mm of rain fell. With only 135.7mm needed over the remainder of the year to surpass this, and November and December's average rainfall totals around 160mm, there is a good chance 2007’s annual rainfall total will also be beaten. Add in that we are in the midst of a La Nina event and it looks even more likely. Should this occur we would be looking at Sydney's wettest year since 1998 when 1648.6mm fell.