One of the basic concepts we learn in a permaculture design course is microclimate. It’s just what it sounds like: variations in conditions from place to place, even if the places are in very close proximity.

One way to experience huge variations in microclimate is to walk around a building. It can feel sunny and tropical on one side of the building, and downright arctic and blustery on the opposite side. Sun, wind, humidity, light-reflecting objects (such as bodies of water and light-colored surfaces), thermal masses (such as asphalt and concrete, and bodies of water) are all factors.

Temperatures can vary significantly across a wider local area too. According to official weather-station readings, our city had a hard freeze last night, 28 degrees, lasting about 7-8 hours. The weather station is about 3 miles inland. Here by the ocean we are always a few degrees warmer than the official reading. The night before last, when the official reading was in the low 30s or high 20s for several hours, we didn’t get any sign of a freeze except a skim of ice on the birdbath.

Last night was another matter. We definitely got a freeze. The birdbath, which is on the west side of the house, is frozen solid. Also there is visible damage to leaves of some plants. On the north side of the house, there’s about a 1/4-inch shell of ice on the water in the rain catchment tubs. And yet, on the sunny south side of the house, there is not a trace of ice in the water.

The concept of microclimate is hugely useful and widely applicable not only in the tangible physical world, but also in our “invisible structures” — the intangible aspects of the human-built environment: social groups, workplaces, congregations, nonprofit organizations, neighborhoods, and so on.