Step 1: Air at 20 °C at sea level rises up a 3 km mountain. Estimate its temperature at the top (dry, then saturated below 1.5 km for the moist part). Step 2: Dry adiabatic lapse rate ≈ 9.8 °C/km. If dry all the way: T = 20 − 3×9.8 = −9.4 °C. Step 3: Realistic: saturated above the lifting condensation level (~1 km). Dry for first 1 km: 20 − 9.8 = 10.2 °C. Moist (~6 °C/km) for next 2 km: 10.2 − 12 = −1.8 °C. Step 4: Descending the far side (dry, moisture rained out): warms at 9.8 °C/km → −1.8 + 29.4 = 27.6 °C — the foehn/chinook effect: warm dry wind. Step 5: This is why windward slopes are green and leeward slopes are deserts (rain shadow). Result: ~−2 °C at the summit, ~28 °C descending — mountains make their own weather via the lapse rate.