Strong winds swept across Delhi on Tuesday morning, raising dust and affecting air quality as well as reducing visibility to 1,000 metres, the India Meteorological Department said. Satellite pictures released by the meteorological office showed a thick layer of dust covering large parts of northwest India. Meteorologists have attributed the dusty conditions to a combination of intense heat in northwest India over the past five days, parched soil due to the absence of rainfall and strong winds that have persisted since midnight.