This is the 11818th most frequent Russian word.
замерзает
"Freezes" or "is freezing."
The word 'замерзает' here is used to describe the process of freezing as an annual occurrence during winter months.
Вода в реке зимой замерзает.
The water in the river freezes in winter.
In this case, 'замерзает' indicates that the tea is in the process of freezing due to the cold temperatures.
Он заметил, что его чай постепенно замерзает из-за морозной погоды.
He noticed that his tea is gradually freezing because of the frosty weather.
Here, 'замерзает' is used to describe the sensation of the face becoming extremely cold due to exposure to low temperatures.