It is officially the hottest AFL grand final.
The temperature at the Melbourne Cricket Ground, where the Hawks and Eagles are locked in battle, has topped the previous hottest game-day record of 30.7C set in 1987.
The Bureau of Meteorology website says the temperature hit 31.3C at 3.12pm in the city's Olympic Park sports precinct, and the mercury is still climbing.
The daytime maximum was expected to go one or two degrees over 30C.
Forecaster Rod Bickson said high temperatures are not that surprising for this time of year.
"It's not unprecedented," Mr Bickson told AAP.
"It just happens to have fallen on a public event."
Some commentators say the hot weather could play into the hands of WA's heat-hardened West Coast Eagles players, though there was no sign of this as Hawthorn jumped out to an early, healthy lead.
