They weren't frozen in the sense of people covered with ice.
The lake is covered with ice for 10-11 months in a year.
We know there was a city to the north which is now covered with ice.
Because of this the street was never covered with snow or ice during the winter.
The only time I ever get really worried is when the trees are covered with ice.
Now most of the land is covered with snow and ice.
The sea is covered with ice most of the year.
The lake at the center of the park could well have been covered with ice in another December.
In early summer the coast could still be covered with ice.
"What if the glass was covered with snow or ice?"