October to April: the exterior window
Winter also brings the UAE's only meaningful rain. It is rare, but a surprise shower on a half-cured exterior coat means redoing sections, so decent crews watch the forecast in January and February and build a buffer day into multi-day exterior jobs. If a vendor quotes a tight three-day window for a full villa exterior in peak winter, ask what happens if it rains.
Practical advice: if your villa exterior is chalking (a powdery residue when you rub the wall), cracking at the parapets, or streaked below the AC condenser lines, get quotes in September and book for October or November. Waiting until March means competing with everyone who had the same idea, and April risks the first serious heat arriving mid-job.