Another manifestation of the heat balance effect is the increase in altitudinal tree lines as latitude decreases in the Northern Hemisphere from the subarctic to the subtropical. In general, tree form is possible wherever the mean temperature for the month of July is equal to or greater than 10 °C (50 °F). A somewhat better fit can be obtained by using the point where the daily maximum temperature is greater than or equal to 11.1 °C (52 °F) during the growing season.

The low temperatures in the Alpine environment stem from the decrease in temperature with elevation: warm air rises; as it does so, it expands and cools. The expansion requires work (in the form of heat) to be expended in the process, and temperature drops. In general, there is a 1 °C drop in temperature for every 100-metre rise in elevation (or, roughly, 2.5 °F for every 500 feet). However, the temperature drop varies somewhat with conditions on individual mountains (e.g., wet versus dry mountain ranges). Larger mountain massifs also show a smaller drop in temperature with increase in altitude. This is because the air mass impinging on the large massif must rise over the entire structure, and the air mass does not cool as much as when only a portion of it rises over a smaller or more isolated mountain. As a consequence, timberlines are higher on a larger mountain range for a given latitude, location, and climate. Nevertheless, other factors, such as radiation, moisture, cloudiness, wind, snow and snow blast, ice, and physiography, affect tree lines to various degrees.