Mist arising from the 'lava lakes'

In ancient times these now flat playing fields were lakes of hot lava. As the volcanoes became dormant basalt bottoms broke, and over many centuries the lakes became swamps. As Tamaki Makarau became Auckland, the swamps were drained, earth was laid and playing fields emerged. 

One might fancy that the rising mist is the result of expelling air by the ancient dragons waiting below.