Reading the Summer Heat

The thermograph at Ashgrove Hill has now drawn forty-one summers, and laid end to end the rolls of paper would reach from the hut to the dam. I know because we measured, the way you measure things when the rain has stopped.

Heat behaves differently in the vale than on the ridge. The valley floor holds a still, heavy calm through the afternoon while the ridge pasture catches every breath that moves. Visitors ask which reading is "right". Neither. Both. The difference is the story.

What the rolls show

The warm weeks arrive in two shapes. There is the long flat summer high, days of small drift, and there is the sharp spike that comes up from the southwest and leaves within thirty-six hours. The spikes make the records. The flats make the summers.

A hot day writes one line. A hot week writes a biography.

Why the floor stays calm

Cold air drains downhill at night, and on clear evenings the vale collects it like a bowl collects water. By dawn the floor sits under its own private winter while the ridge is ten degrees warmer. The frost advisory tonight is really a map of the hollows.

Forty-one summers of this pattern, and the advice hasn't changed: watch the hollows, trust the screen, and doubt any forecast that forgets where the cold goes when the sun goes down.