New Delhi, Oct. 31 -- A spell of heavy rain, rare for October, washed the pollution out of Delhi's air on Friday and gave the Capital its cleanest October day in four years. Residents woke to a cold, wet morning, and the temperature rose no higher than 20.7degC, the lowest October maximum in records going back to 1951. With Friday's official air quality index (AQI) reading of 60, Delhi is poised to record its cleanest October since the Central Pollution Control Board began its daily AQI bulletins in 2015. The average for the first 30 days of the month stands at 167. Friday's maximum was 10.3 degrees below normal. Safdarjung, the city's base weather station, recorded 61.4mm of rain in the 24 hours ending 8.30am on Friday, the sixth-highest 2...