PETALING JAYA: A heavy downpour early this morning caused massive traffic delays along major roads in the Klang Valley. Hundreds of motorists were caught in a traffic gridlock at the NKVE-bound stretch of Jalan Lapangan Terbang Subang due to flash floods. A Fire and Rescue Department spokesperson said the flood waters had risen from 0.3m up to 0.6m between 7.30am and 8.20am due to the teeming downpour. He said the flood lasted for about an hour and receded at 8.20am when the rain eventually stopped. National Flood Monitoring Centre on its Facebook page Public Info Banjir also warned residents at several areas in Klang Valley to exercise caution. The heavy rain, it said, had caused water levels at rivers in the Klang Valley to rise. The Malaysian Meteorological Department on its Facebook page also warned Malaysians of heavy rain and thunderstorms in several districts of Selangor such as Petaling, Kuala Selangor, Gombak, Hulu Selangor and Klang besides at Kuala Lumpur and Putrajaya. While flash floods hit several parts of the Klang Valley, the people sighed a relief with the haze situation improving after air quality was reduced to unhealthy levels in four places in the Klang Valley and Negri Sembilan as at 9am today. The Department of Environment website said Nilai in Negri Sembilan had an Air Pollutant Index reading of 118. The API was 123 at 6am. It said the API was 105 in Shah Alam at 9am, 102 in Putrajaya and 101 in Banting, Selangor. An API reading of 0 to 50 indicates good air quality; 51 to 100, moderate; 101 to 200, unhealthy; 201 to 300, very unhealthy and 300 and above, hazardous.