On Sunday September 17th, thousands of runners and supporters will descend on the Harbour City for the 2023 edition of the Sydney Marathon, and it's shaping up to be a hot one.  

The Sydney Marathon event includes a range of race distances, from a 3.5km family-oriented fun run right the way through to the full 42.195km marathon, which attracts elite runners from all around the world. This year also marks the beginning of a three-year bid to elevate the Sydney Marathon to "Majors" status. If successful, this would put the Sydney Marathon alongside the likes of the Tokyo Marathon, Boston Marathon and Berlin Marathon. Let's look at what weather conditions runners and spectators can expect on the day. 

Image: Runners enjoy a traffic-free crossing of the Sydney Harbour Bridge. Source: Sydney Marathon Instagram (@sydney_marathon)

Races start in Milsons Point and runners are treated to a crossing of the iconic Sydney Harbour Bridge in the first few kilometers of their run. The first race to start is the Sydney Marathon 21.1km (previously known as the “Half Marathon”), which commences at 5:45am, and all races are underway by 8:30am. Current models suggest there will be some significant warmth for this early in spring for the Sydney Basin. Temperatures of 17-19°C are expected for the start of the races and will warm to a top temperature of around 28°C during the early afternoon. Whilst most races will be wrapped up by that time, the tail of the Sydney Marathon will still be on the course. This heat will add to the challenge at the end of the 42.195km course. For perspective, an average September day in Sydney has a low of 11°C and a high of 20°C, so the expected temperatures are around 8°C above this. 

Image: Forecast maximum temperatures for the Sydney Basin according to the ECMWF model.

Clear, sunny skies are expected throughout the day and there are no indications of any rain. Given the expected warmth though, I'm sure some runners may have appreciated a light cooling shower or two. Winds are expected to be mostly light and out of the west-northwest throughout most of the events, with a northeast sea breeze developing during the afternoon. Whilst this sea breeze may bring some cooling it will also bring higher levels of humidity.  

Good luck to all competing and be sure to stay hydrated during your run.