Melbourne is having such a wet year that it will exceed its annual average rainfall total by the end of this week.

As of 9am on Tuesday, October 13, Melbourne had registered 647.4mm of rain so far this year. The city's long-term annual average is 648.3mm.

Image: One of Melbourne's wet mornings in 2020. Source: @walking_perspective / Instagram

Two rain-bearing cold fronts will cross Victoria between Thursday and Saturday, collectively delivering enough wet weather to make up the 1mm needed for Melbourne to exceed its long-term annual average. In fact, the city could pick up more than 20mm between now and Sunday.

So, how does this year stack up against Melbourne's long-running historical rainfall record, which dates back to 1855?

The current year-to-date rainfall (as of Tuesday) is the city's highest running annual total to this point in October since 1996. In 165 years of records, only 11 have had more rain up to this point in the year, with 1911 (785.9mm) the wettest.

Melbourne's water storage level is currently at 73.6 percent of capacity in response to the recent rain. This is the highest level for this point in the year since 2014.

For this to become Melbourne's wettest year on record, the city will need to amass another 320.2mm by the end of December. For context, the long-term average for October, November and December combined is 185.4mm. It's a tough ask, but not impossible.