Read the colours
Snow index, from 1 to 100
These colours show the Normalized Difference Snow Index (NDSI), which uses reflected light to help identify snow. The numbers are an index, not snow depth or a percentage of ground covered.
- 1–20
- 21–40
- 41–60
- 61–80
- 81–99
- 100
Swatches sample NASA’s palette; shades vary within each range. See the full NASA colour key.
What if there is no colour?
The reference map can show through where the overlay is transparent. That includes a zero index, cloud, night, water, missing data and other masked values. This view cannot tell you which reason applies to a blank patch.
Try a small observation
Describe one patch
- Choose a region and find a coloured patch, if one is visible.
- Match its shade to the key. Does it form a narrow band, scattered patches or a larger area?
- Switch the snow colours off to find the place on the reference map, then switch them back on.
How could I describe it?
“Near this place, I can see a band of pink snow-index colours. The nearby uncoloured area could have several explanations; this view alone doesn’t tell me whether it has snow.”
If you find no coloured patch, try another region. No visible colour is still an observation, but it is not proof that snow is absent.