Certified GKH Gardening Expert
The answer is a bit complicated, because there are multiple types of clematis which should be pruned at different times of year. Pruning in February is safe for most clematis, but for those on pruning group 1, pruning in February will remove next year's flower buds. If you don't know what type you have, you could wait till your clematis flowers next year and prune immediately after the flowers fade.
These articles explain the issue: