Sydney is in for some unseasonably warm days, with temperatures set to hit 23 on Friday and 25 on Saturday, according to Weatherzone meteorologist Tom Hough.
"If we see 25 on Saturday it will be seven above average for this time of year," he said.
But a cold front set to move through late on Saturday will bring it back down to the average, 17, for Sunday.
It will be a relief to City2Surf runners, who'll not only have cooler temperatures for their run, but a "pretty breezy" westerly wind helping them along, around 30km/h.
- Weatherzone is owned by Fairfax Media