h -- Cloud base of lowest cloud seen (meters above ground)

0 -- 0 to 50 m
1 -- 50 to 100 m
2 -- 100 to 200 m
3 -- 200 to 300 m
4 -- 300 to 600 m
5 -- 600 to 1000 m
6 -- 1000 to 1500 m
7 -- 1500 to 2000 m
8 -- 2000 to 2500 m
9 -- above 2500 m
/ -- unknown