Grade of cold air | Division of grade |
General cold air | (6 ≤ Dt48 < 8) or (Dt48 ≥ 8 but Tmin>8 ) |
Strong cold air | Dt48 ≥ 8 and Tmin < 8 |
Cold wave | (Dt24 ≥ 8 or Dt48 ≥ 10 or Dt72 ≥ 12) and Tmin < 4 |
Strong cold wave | (Dt24 ≥ 10 or Dt48 ≥ 12 or Dt72 ≥ 14) and Tmin < 2 |
Extreme cold wave | (Dt24 ≥ 12 or Dt48 ≥ 14 or Dt72 ≥ 16) and Tmin < 0 |