Short answer: a frost delay is when a course holds all play until frost melts off the turf. Walking on frosted grass ruptures the frozen plant cells and kills the blades, leaving brown footprint trails on greens for weeks. Delays typically last 30 minutes to 2 hours after sunrise.
Grass blades are about 90% water. When frost forms, ice crystals form inside the leaf tissue; foot or cart traffic crushes those crystals through the cell walls. The damage isn't visible immediately — it shows up days later as blackened, then brown, turf. A single foursome walking a frosted green can leave hundreds of dead footprints.
Even after the delay lifts, cold mornings change the math: the ball compresses less and flies shorter, and firm greens reject high approaches. See is it too cold for golf? for temperature thresholds and distance-loss numbers.