Why do tropical mountains have frost at night throughout the year?

Tropical mountains experience frost at night throughout the year primarily due to the effects of altitude on temperature. In these regions, atmospheric temperature drops as elevation increases, typically by about 0.5 to 0.6 °C per 100 metres.1

At high altitudes in equatorial regions, the lack of seasonal variation means that while days can be warm under the intense tropical sun, temperatures at night consistently drop to levels that allow frost to form. This creates a unique local climate often described as "winter every night and spring every day".1

Additionally, on clear, calm nights, the ground undergoes radiational cooling, where heat is lost from the surface to the atmosphere. In the absence of significant cloud cover or moisture to trap this heat, surface temperatures can fall below freezing, leading to the formation of frost regardless of the time of year. This phenomenon is distinct from temperate mountains, where frost is governed by seasonal changes rather than a daily cycle of intense solar heating followed by rapid nocturnal cooling.213