Microclimate is the local weather of a particular patch of ground, and it can differ by 5-10 degrees Celsius in winter minimum temperature between two sites only a kilometre apart. Wind exposure, sun exposure and cold-air pooling are the three features to read at a site, and all three can be observed with no instruments.
The small-scale weather of a site, produced by its slope, shelter and position, as distinct from the regional climate.
The Regional Climate Is Only the Starting Point
The region’s climate tells you roughly how cold winters get and how much rain falls. The microclimate decides how much of that you feel. The carrier states that microclimate varies dramatically within a few hundred meters, and two sites a kilometer apart can differ by 5-10 degrees Celsius in winter minimums. That is the difference between a frost that kills the tender crops and one that does not, and between a house that is cheap to heat and one that is not.
Three Things to Read
- Wind — where it comes from and what shelters you. See Prevailing Wind Patterns.
- Sun — how much light reaches the ground in winter, and what shades it. See Sun Exposure & Shadows.
- Cold air — where it pools on still nights. See Cold Air Drainage & Frost Pockets.
How They Combine
A gentle south-facing slope (north-facing in the Southern Hemisphere) that is sheltered from the prevailing wind and above the valley floor gets the most winter sun, loses the least heat and escapes the frost pockets. The same region has hollows that are cold and shaded and hilltops that are windy. The ideal is a middle position, which is why the carrier recommends building on slopes, not valley bottoms or ridgetops, for living quarters and tender crops.
What You Need
- A thermometer, ideally one that records the minimum — or a cheap pair of them to compare two spots on the same night.
- Observation across seasons — one visit shows one weather.
- Local knowledge — ask where frost comes first and where snow lies longest.
Method: A Simple Comparison
Step 1: Pick two or three candidate spots One high, one mid-slope, one low.
Step 2: Compare on a clear still night Read the minimum at each spot at dawn. Clear, calm nights show cold-air pooling most clearly.
Step 3: Look at the plants Frost-damaged leaves, late-melting snow and late-leafing trees mark cold spots.
Step 4: Combine with wind and sun notes Keep a note per site. See Terrain & Soil Analysis for the ground itself.
Common Mistakes
- Judging from a summer visit — winter is what separates good sites from bad.
- Choosing a sheltered hollow — it is also the coldest and dampest spot.
- Ignoring wind — constant wind wastes heating fuel, as the carrier notes.
Safety
Exposure kills in cold, wind and heat
Do not carry out night comparisons in freezing weather without shelter, fire and a partner, and do not leave children or the sick in an unprotected site while testing it.
What’s Next
- Learn next: Prevailing Wind Patterns — wind first, because it is the easiest to read
- Combine with: Passive Solar Building Design — using the sun the site gives you