Forecaster Fan Junhong started learning to ski in January, and has progressed quickly enough to ski down the hill unaided now.

"It is convenient to use skis to collect data and experience the weather on the pistes and runs," the 51-year-old said.

Li said it is necessary to monitor and note all the weather factors, because each of them can make a major difference during competitions. The quality of snow and the wind direction can affect the athletes' performances, while temperatures and wind speeds may pose safety risks.

"For example, ski jumpers depend heavily on the wind to keep their bodies stable and help them go faster. If the wind speed exceeds 3 meters per second, these athletes will be affected. Head winds can help lift jumpers, which is what they want, while tail winds can put them under pressure and disturb their performance," he said.

The Winter Games is more demanding in terms of weather than its summer counterpart, and requires a more-targeted service, such as precise information about snow depths.

To obtain such information, the forecasters stay at a chalet on the mountain after they have predicted the snowfall. Usually, four work as a team to collect and analyze snowfall data, with one person working outside each hour until the snow stops.

If it snows at night, they concentrate on their work and don't sleep.

The forecasters collect snowflakes and analyze their appearance to gain a better understanding of snow depths, which affect competitions, and offer advice that aids maintenance of the runs.

Liu Huayue spent the night of Jan 5 assessing snowflakes through a microscope to garner clues about the likely snow depth the next day.

"If the snowflakes have obvious hexagonal branches it means the particles are large, so the snow will be deep. Even during the same snowfall, depths may differ due to the different shape of the snowflakes. During the Winter Olympics, if the snow exceeds a certain depth, some events such as cross-country skiing may be delayed or even canceled," the 30-year-old said.