NEW DELHI: Delhi experienced a sharp cold spell on Monday as the minimum temperature dipped to 3.6°C in parts of the city, with isolated cold-wave conditions recorded. Safdarjung, the city’s base station, logged 4.2°C – four degrees below normal – making it the coldest Republic Day since 2021, when the capital had witnessed 2.1°C.At the same time, the air quality slipped back to the ‘poor’ category, ending a rare two-day stretch of moderate AQI in Jan, with the 24-hour average rising to 241 at 4pm from 153 on Sunday, the lowest Jan reading in four years. Ayanagar recorded the city’s lowest minimum at 3.6°C, while Ridge logged 5.3°C. The two stations met the criteria of cold wave on Monday.Clear skies and persistent northwesterly winds over the weekend contributed to the drop in temperatures. Wind speeds eased on Monday due to an approaching western disturbance, which is expected to raise the minimum temperature and bring light rain on Tuesday, officials said. IMD has issued a yellow alert for Tuesday, forecasting light to moderate rain and snowfall across the western Himalayan region on Jan 27 and 28. Light to moderate rain and isolated thunderstorms or hailstorms are also likely over parts of northwest India.On Tuesday, the minimum is likely to remain between 8°C and 10°C and the maximum between 18°C and 20°C. Centre’s Air Quality Early Warning System expects AQI to improve to ‘moderate’ on Jan 27-28 before turning ‘poor’ again from Jan 29.