New Delhi, Feb. 1 -- The Capital is likely to receive spells of rain on Sunday, with the India Meteorological Department (IMD) issuing a "yellow alert" for the city amid forecasts of thunderstorms, lightning, strong winds and dense fog, even as minimum temperatures continued to dip on Saturday. IMD said cloudy skies will prevail through Sunday, with two spells of rain expected in some parts of the city. "A spell of very light rain to light rain accompanied by thunderstorm, lightning and gusty winds with speeds of 30-40 kmph is likely during the morning to forenoon hours," an IMD official said. The rain activity is being triggered by the influence of another western disturbance affecting northwest India, IMD said. Delhi has already seen the impact of multiple such systems this month, with the Safdarjung weather station recording 25.4 mm of rainfall in January - around 38% more than the long-period average of 18.4 mm for the month. Meanwhile the minimum temperature dropped to 6.7 degrees Celsius (degC) on Saturday, one degree below normal.However, IMD has forecast a sharp rise in night-time temperatures on Sunday with the persistent cloud cover trapping some of the day's heat. Gurugram, meanwhile, logged 6.6degC on Saturday. "The minimum temperature is expected to be around 10-12degC on Sunday and 11-13degC on Monday. It is likely to fall again to around 7-9degC by Thursday," the IMD official cited above said. January has seen sharp fluctuations in night temperatures, including four days of cold wave conditions earlier this month. Delhi's maximum temperature on Saturday was recorded at 21.5degC, about 0.8 degrees below normal. It is expected to fall to between 17degC and 19degC on Sunday. Gurugram saw a maximum temperature of 20.1degC on Saturday. IMD said shallow to moderate fog conditions are also likely to persist during the morning hours through the early part of next week. Delhi's air quality deteriorated further on Saturday, slipping back into the "very poor" category. The city's 24-hour average air quality index (AQI) stood at 315 at 4 pm, compared with 253 recorded at the same time on Friday, according to the Central Pollution Control Board (CPCB). Gurugram saw a "poor" AQI of 300 on Saturday at 4pm, significantly higher than Friday's 268 (also at "poor" category). Forecasts by the Air Quality Early Warning System for Delhi (AQEWS) indicate that air quality is likely to remain in the very poor category from Sunday through Thursday. "The outlook for the subsequent six days suggests air quality will fluctuate between very poor and poor," the AQEWS bulletin issued on Saturday evening said....