LUCKNOW, Dec. 19 -- A thick blanket of dense to very dense fog brought much of Uttar Pradesh to a near standstill on Thursday, prompting the India Meteorological Department (IMD) to issue red and orange alerts for several districts and warn of cold to severe cold day conditions over the next two to three days, officials said.

The IMD's meteorological centre in Lucknow said fog intensified due to an inversion layer in the lower atmosphere, an anti-cyclonic circulation over western and adjoining central India, and the influence of a tropical westerly jet stream over north India. These conditions caused persistent daytime fog and a fall in maximum temperatures across many areas over the past 48 hours.

"The prevailing conditions are likely ...