The construction timetable of the new café at the top of Snowdon has slipped by up to two weeks due to high winds, says Snowdonia National Park Authority.
But the roof is on the building and the authority said it was hopeful the work could be back on schedule within weeks.
The former cafe at the summit of the highest peak in England and Wales was once described by Prince Charles as "Wales' highest slum".
The Hafod Eryri visitor's centre is being built at a cost of £8.35m.
The café sited 3,500 ft (1,067m) above sea level and weather conditions there can often be more extreme than at lower altitudes.
The Snowdonia National Park Authority said the bad weather earlier this summer had made the building work difficult at times, and it has praised the work of the construction staff as "heroic".
It said strong winds during July had slowed down efforts to put on the roof, to the extent that by the end of the month the construction schedule was around two weeks behind.
The authority's website shows park authority members in low cloud during a site visit last month to inspect progress.
Chief executive Aneurin Phillips said: "From the onset, we knew that the contractors faced a difficult task in undertaking such a project as this and we were obviously concerned with the extreme weather on the summit.
"Heavy rain, strong winds and exposure during the last few weeks has unavoidably affected some of the building work."
He added that the authority was already looking forward to the official opening of Hafod Eryri in July 2008.
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