Grade 9 Earth Science · Field Demonstration
Dew,Frost & Fog
Three ways a Philippine night turns air into water — witnessed from the rice terraces of Banaue to the summit of Mt. Pulag.
Dew
Dew forms when a surface cools below the air’s dew point on a clear, calm night. Water vapor touching that surface condenses into liquid droplets. Grass cools fastest of all — thin blades hold little heat — so dew collects heavily on lawns and rice leaves, almost never on concrete.
Dew on the palay most highland mornings — a free source of extra moisture during dry spells.
Frost
Same conditions as dew, but the surface itself is at or below 0°C. Water vapor skips the liquid stage entirely and converts straight into ice crystals — deposition.
Frost is not frozen dew
Dew only becomes frost if it later freezes — true frost usually forms straight from vapor, without ever being liquid.
Frost with a local name
In Benguet’s highlands, frost is common enough to have a local name — andap. It strikes hardest in the higher towns of Atok, Kibungan, Bakun and Kabayan during the Amihan season, roughly December to February, when official station readings at Benguet State University in La Trinidad have fallen into the single digits °C — cold enough for ground-level surfaces to drop to freezing even when the air itself reads a few degrees above it.
At first light, before the sun hits the ice-coated leaves, highland farmers spray their crops with water from hoses and sprinklers to prevent “frost burn.” La Trinidad’s strawberry farms — the ones tourists visit for the picking — sit in this same frost-prone belt.
Coldest spot in the Philippines. 2,922 MASL, a record low of −2°C in December 2015, and the “sea of clouds” hikers see from the summit at sunrise.
Fog
Fog is a cloud that never left the ground. Humid surface air cools until its water vapor condenses around microscopic dust or salt particles suspended in the air — condensation nuclei.
Kennon Road
The historic route up to Baguio is officially logged as one of the most accident-prone roads in the country — sharp blind curves with fog rolling in most afternoons, cutting visibility to almost nothing. Local advisories exist specifically warning motorists to slow down when the fog sets in.
Fog nearly every clear, cool morning.
Ridge-top mist that can swallow the Taal Lake view entirely within minutes.
So exposed to fast-moving weather that flights in and out of Basco airport are among the most frequently weather-cancelled in the country.
The Four Golden Clues
Seven Sites
Every location on this map has been logged in the case file. Select a pin to read its evidence.
Tap a pin to fly down to the site — 7 on record
The Case Is Now Yours
Your Final Case Report is waiting. Compare notes with your squad, lock in your answers, and see who earns the Certified Weather Detective badge.
Grade 9 Earth Science · Weather Detectives: The Mystery of the Morning Vapors · Field Demonstration
