Thiruvananthapuram: The India Meteorological Department (IMD) has issued a weather forecast on Friday (May 29), placing several districts in Kerala under a yellow alert. The “Be Prepared” warning means there is a chance of isolated heavy rainfall in parts of the state.

Kozhikode district is under a yellow alert for May 29, indicating the possibility of heavy rain in isolated areas. The IMD defines heavy rain as 64.5 mm to 115.5 mm of rainfall in 24 hours.

On the same day, heavy rain is “Very Likely” in Thiruvananthapuram, Kollam, Pathanamthitta, Alappuzha, Kottayam, Ernakulam, Idukki, Malappuram, Kozhikode and Wayanad. Thrissur, Palakkad, Kannur and Kasaragode are under a green alert, meaning only light to moderate rain is expected.

The IMD says “isolated” rainfall means it may occur in only 1% to 25% of weather stations in a district, so not every area will be affected equally.

Rain forecast for Kerala

From May 30 (Saturday), rain is expected to reduce in most districts, with light to moderate showers. However, Pathanamthitta, Alappuzha and Kottayam may still receive heavy rain in isolated places.

On May 31 (Sunday), the yellow alert area is expected to increase again, covering Pathanamthitta, Alappuzha, Kottayam, Ernakulam, Malappuram and Wayanad.

From June 1 onwards, rain is expected to continue in many districts. The IMD has flagged Thiruvananthapuram, Kottayam, Ernakulam, Idukki, Malappuram, Kozhikode and Wayanad for isolated heavy rain.

On June 2, the alert area expands further, covering Thiruvananthapuram, Kollam, Alappuzha, Kottayam, Ernakulam, Idukki, Malappuram, Kozhikode, Wayanad, Kannur and Kasaragode.

How IMD classifies rainfall

The IMD defines rainfall levels as follows: light rain is 2.5 mm to 15.5 mm in 24 hours, moderate rain is 15.6 mm to 64.4 mm, and heavy rain is 64.5 mm to 115.5 mm. Very heavy rain ranges from 115.6 mm to 204.4 mm in 24 hours.