At 403 mm till Thursday afternoon, it is the maximum rainfall recorded in the month since 417.3 mm in September 1944.
The alert has been sounded in Idukki, Kottayam, Kasaragod, Kannur, Kozhikode, Wayanad, Malappuram, Thrissur and Ernakulam districts for the next two days.
While issuing its forecast for September, IMD Director General Mrutunjay Mohapatra on Wednesday said the shortfall recorded during August is likely to be compensated with excess rainfall in the current month.
A red alert has been issued for Sholayar, Peringalkuthu, Kundala, Kallarkutty, and Moozhiyar dams.
Heavy rainfall was reported at Vaikom in Kottayam district where 10 cm rain was recorded, followed by Kakkayam in Kozhikode and Vellarikkundu in Kasaragod with 8 cm each.
An orange alert (heavy to very heavy rains) has been issued in Idukki and Wayanad districts for three days (August 28, 29, 30).
Yellow alert in Alappuzha, Kottayam, Idukki, Palakkad, Malappuram and Kasaragod districts on Thursday, August 26.
The India Meteorological Department (IMD) said Delhi recorded 139 mm of rainfall, the highest one-day rain for August in at least 13 years.
Kerala is likely to not see heavy rainfall until August 20. However, the state is likely to see a spell of normal rainfall in the next two days.
Only Pathanamthitta, Kottayam and Ernakulam districts received near-normal rainfall.