Meteorology · Optical — Halo and Forecast Value
A halo around the sun or moon (from cirrostratus ice clouds) often indicates:
- AAn approaching warm front and deteriorating weather within a day or so✓ Correct
- BImmediate clearing
- CAn approaching hurricane within an hour
- DNo weather significance
Explanation
A halo is produced by ice crystals in high cirrostratus, the leading cloud of an advancing warm front. The thickening, lowering cloud sequence (cirrus → cirrostratus halo → altostratus → nimbostratus) often heralds rain and wind within a day — 'ring around the moon, rain soon.'
Authority: Bowditch (Pub. No. 9); weather lore with basis
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