Impersonal verbs are only used in 3rd person singular (preceded by pronoun "il": il pleut).
This is the case of verbs: brouillasser, bruiner, brumasser, brumer, crachiner, dracher, gouttiner, grêler, neiger (and its derivatives), neigeoter, pleuvasser, pleuviner, pleuvioter, pleuvoter, pluvioter, pluviner, vaser, venter, verglacer.
In the sense "to rain", the verb flotter is only used in 3rd person singular: il flotte.
The same is true for glacer in the sense of "freeze" (il glace) and grésiller in the sense "it's hailing".
16 verbs follow this model. Below an extract:
To see other models, refer to Model Table
Based on the ending, you can identify features that different verbs have in common. Click on the verbs above to see their conjugation tables and explore their conjugation patterns.