I know Esperanto's like French in that there's no perfect or pluperfect progressive, that to render a phrase like

It's been snowing for 5 days

one would use the present tense and de or dum and say

Neĝas de 5 tagoj

But how would one express the same idea without a start time, like

It's been snowing all week

or just

It's been snowing

In French, one apparently uses the passé composé followed by "and continues" in the present tense:

Il a neigé toute la semaine et ça continue

How's it done in Esperanto?

Some alternatives:

neĝas jam unu semajnon (it's been snowing for a week already)

neĝas jam tutan semajnon (it's been snowing for a whole week already)

Adding -ad- to the verb gives it
the nuance of "it's never stopped":

neĝadas jam unu semajnon (it's been snowing continuously for a week)

neĝadas jam tutan semajnon (the snow hasn't let up for a whole week)

noelekim:Adding -ad- to the verb gives it the nuance of "it's never stopped"

Excellent point. I never noticed before that the frequentive aspect of -ad- can be tantamount to a perfect progressive. Thanks much for the tip!

The perfect progressive in English doesn't necessarily imply that the action is occurring at the moment of speaking. For example, I have been seeing a lot of Jane lately; We've been having trouble with the boiler.

Continousness can come from repetition as well as uninterrupted duration. This meaning can be captured or emphasised with -ad. But it doesn't seem to me to be quite as ordinary in Esperanto as the progressive verbs forms are in English.

Neĝadis(as) jam unu semajnon is certainly possible but insists on the frequency of the snow showers (or no let-up) more than the progressive does in English.

Looking out of the window at the snow falling, I think I could just as well say neĝis jam ... as neĝas jam .... Do the French really find it necessary to add et ça continue? It seems somewhat cumbersome.