Work on the Snowdon summit building is being hampered by snow, says the Snowdonia National Park Authority.
Workers on the project have had to dig snow off the railway track just to get to work every day.
The contractors have had to concentrate instead on work inside the building because of the harsh conditions at the summit.
A spokeswoman for Snowdonia National Park said there was still three months work to complete the £8.35m building.
"Due to the amount of snow that has fallen on the summit within the last few weeks, attempts by workers to reach the summit have been hampered," said the park authority's Llinos Angharad.
"When they do succeed in reaching the summit, conditions continue to be difficult for them to complete the stonework on the outside of the building as the snow, ice, rain, must and the general dampness in the air makes it difficult for workers to work with the stone," she added.
Despite the weather problems, she said there was not a problem with completing the building, which is called Hafod Eryri, before the autumn deadline to draw on funds from Europe.
The assembly government has supported the project and backing has also come from European Objective One funds. A public appeal also raised £350,000.
"The authority is immensely grateful for the dedicated and determined efforts the workers are making to complete the building.
"The weather conditions are atrocious for them, but they persist in their efforts on our behalf," Ms Angharad added.
The building will replace the demolished mountain cafe which was once called Britain's highest slum by Prince Charles.
Once completed, the cafe will look like this
The old summit building was built in 1935 and designed by Sir Clough Williams-Ellis, the founder of the Italianate village Portmeirion a few miles away on the north Wales coast.
The centre will have facilities giving visitors the chance to learn more about Wales' highest mountain and its environment.
It will also provide weather information, advice on routes as well as refreshments and shelter
The café sited 3,500 ft (1,067m) above sea level and weather conditions there can often be more extreme than at lower altitudes..
Last summer the project was delayed by high winds.
The building's name was closen after a secret ballot. Eryri in English is Snowdonia but there is no translation for Hafod, an old Welsh term for residence on high land.