Dozens of sensors dotted around the 12th-century monument have shown no indication that it is deteriorating, but architect Philippe Villeneuve is worried.
Mr Villeneuve said Wednesday that the stone walls are still saturated with water sprayed by firefighters during the 15th April blaze.
He said they could dry too fast amid the record temperatures expected in Paris this week.
He said so far the masonry is stable but the structure remains fragile.
"What I fear is that the joints or the masonry, as they dry, lose their cohesion...and all of sudden, the vault gives way."
Specialists are working to stabilise the cathedral's structure before reconstruction work begins.
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