A possible thunderstorm could be set to hit Brisbane ahead of tonight's AFL Grand Final, with both Richmond and Geelong on standby for wet and wild conditions during the season's decider.

The Bureau of Meteorology have forecast a 70 percent chance of rain in the afternoon and evening, as well as a 20 percent chance of lightning as the game is due to commence at 6.30pm local time.

Under the AFL's rarely used 'lightning rule', any match can be postponed or stopped mid-game by up to an hour if lightning strikes are determined to be within a 10km vicinity of the stadium.

The rule was enacted during an AFL match between Sydney and Greater Western Sydney in March 2014, when play was delayed by 25 minutes after lightning struck the ground midway through the opening quarter.

Play has also been stopped due to lightning in recent AFLW matches, with a game last delayed due to inclement conditions when Carlton faced Greater Western Sydney in February 2018.

This season's night games in Queensland have been marked by humid and dewy conditions, which are again expected throughout the first ever Gabba Grand Final on Saturday evening.