Minimum temperatures fell appreciably in various parts of the state, the MeT office here said.
The lowest minimum temperature was recorded in Muzaffarnagar at 6 deg C, it said.
Night temperatures witnessed a sharp dip in Varanasi, Allahabad, Agra, Meerut divisions, it said, adding that the mercury, however, rose in Gorakhpur and Faizabad divisions.
In Lucknow, the district administration ordered the closure of all schools up to Class VIII till January 10 in view of the continuing cold conditions while classes above VIII would not start before 9 AM.
They warned that dense fog may occur at isolated places in the state.