The roof and steel structure for the building at Hafod Eryri are complete and the interior of the building is almost finished but work on the granite cladding is still underway. But the contractor said work was held up last winter.
"We have had to face problems and conditions on this scheme which are as unique as the location itself," said Carillion regional director Meirion Evans.
"We have found solutions and worked extremely hard every moment the mountain and conditions will allow. I am aware that people will be disappointed at the delays which mean that plans cannot be laid with certainty for opening Hafod Eryri to the public."
Four feet of snow in April was followed by heavy rain and winds regularly gusting over 129km/h.
Last year, at the key peak period of summer, 85 days were lost and since March this year 70 days have been lost because of the weather.
Over £4M of the £8.1M project is being financed by the Welsh European Funding office, but according to the project website the new building must be completed no later than early summer 2008 to qualify for the European funding.