This is a question that has confused me for a long time. I understand why typically the higher up you go, temps will get lower (exponential pressure decrease). And I understand that the cold air pools in valleys. However, I live in a small valley (about 150ft deep), I am at about 1500 ft (top of the ridge is about 1650) and the top of the mountain is about 4000 ft and the valley floor is about 1000ft. Does this mean my hillside valley gets the coldest? Since I have elevation & valley effect?

2 Answers 2


Probably, yes you will the colder spot around. But a lot depends on how the sun is shining on your place and where the trees are. Trees have another effect too. They can block/slow the cold air (and fog) from rolling away.

  • Thank you! There's trees on the N and SW side. This is helpful to know, since this is a pretty temperate area (9b) so I want all the chill I can get for apples etc.
    – Fix4Dirt
    Jan 20 at 22:39
  • 1
    Apples in Florida, California, or New Orleans are unheard of. Can always try a few low-chill apple trees before planting acres of them. Citrus, Avocado, Palms more likely. Jan 21 at 1:35
  • Gala does well here actually!
    – Fix4Dirt
    Mar 2 at 3:42

It is more complex than that.

If you do not live at equator (or in tropical regions), you never have the Sun above the terrain, but at an angle. So exposure (orientation) is very important: on some hillside you may have much more sun and so heat. (photovoltaic panels are placed on a angle for a reason). OTOH on there are other orientations which have the negative effect. (You will see much more diversity on wild flora). And it varies during season, so check if you want a seasonal best (e.g. when some plants have leaves) or yearly best (e.g. for some other trees).

And there are many other climate effect (you live near a mountain), so the mountain may block air, or may compress and decompress giving rain or heat, etc. For such effect you need a much larger picture.

So, the rules are very generic (and average, e.g. from both side of a valley), but check carefully your locale climate, I would not generalize too much. Wild flora and nearby plantations (and gardens) may help to assess better the climate.

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