High cirriform clouds are composed almost entirely of ice crystals. In tropical regions, air temperatures low enough to freeze all liquid water usually occur only above 6,000 m (about 20,000 feet). In polar regions, however, these same temperatures may be found at altitudes as low as 3,000 m (about 10,000 feet). Hence, while you may observe cirrus clouds at 3,600 m (about 12,000 feet)over northern Alaska, you will not see them at that elevation above southern Florida.

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Cirriform clouds, including cirrus clouds, are high-level clouds that form above 20,000 feet in tropical regions and can form at lower altitudes in polar regions due to the colder temperatures found at lower heights, supporting the statement about observing cirrus clouds at different elevations in Alaska and Florida.

High Cirriform Clouds Are Composed Almost Entirely of Ice Crystals