Having problem. I did what I thought I needed to do and got a journal entry that DU was destroyed, but the blight storms are still going on and nobody, including Vivec, knows DU got his come-uppance. What could I have missed?

After you have killed Dagon Ur, you should get the FMV cutsceen and Azure(?) should give you another magic item (I can't remember what it is...but I think it is a ring). If you have experienced all these, then you should have ended the main quest.

I know, when I ended the main quest, the blight storm didn't seemed to stop, especially in Ald Ruhn, but Vivec and the citizens of Morrowind did acknowledge my success.

You shouldn't use Intervention or Recall spells to escape the mountain, You should come out as you came in, Then you'll meet Azura and the quest is complete

SPOILER about ending sequence:
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My 2 characters that have finished and now get stuttering commoners saying that "ey..eh..ah.. I do not know how to to talk to the Nevarine..." did the following:

- knocked down Dagoth Ur to zero hit points,
- pressed on into statue room beyond DU's evaporating corpse and
- destroyed the red stone with Sunder and Keening while listening to DU scream at me/blast me with fireballs because of what I was doing,
- DU dies again, for good,
- watched titanic sized robot collapse,
- walked back into the first place I met Dagoth Ur and as I approach the exit door from that room, Azura appears,
- got a ring from Azura and had the curse of the Nevarine lifted
- and continued into mountains to raid.

Anyhow, the red ash storms and red sky are gone after the above sequence, but not the sand storms. I still get sand storms in the ash lands and around Ald'Ruhn/Maar Gan and my Telovanni Wizard character's house.

If you recalled or used intervention then you need to return to Dagoth Urs citadel and talk to Azura, then you will have completed the main quest and everyone else will acknowledge that.

Raktizz