When do I need to worry about Frost
Recognizing frost risk around your plumeria
Plant surfaces can become colder than the reported air temperature, particularly on clear, calm nights. Frost may therefore form even when the forecast temperature remains above freezing. Consider local forecasts, frost advisories, wind, cloud cover, and cold pockets around your plants. Frost and freeze injury involve damaging tissue temperatures and ice formation; sunlight striking visible frost is not an adequate explanation of the damage.
For practical protection steps, see What to do about Frost. For seasonal care, see our Winter Care for Plumeria Guide.
Further reading: Frost and ice — Met Office and Freezing and Frost — University of California IPM.