Socked in

From Glossary of Meteorology

socked in

In the early days of aviation, commonly used to describe weather at an airport when ceiling and/or visibility were of such low values that the airport was effectively closed to aircraft operations.

The term probably originated from reference to the wind sock. When the sock was in the clouds or when the visibility was so badly impaired that the sock was not visible, the airport was "socked in." The expression is still widely used.