Based on rainfall distribution, irrigation pattern, soil characteristics, cropping pattern and other physical ecological and social characteristics, Tamil Nadu State is classified into seven distinct agro-climatic zones delineated as follows:
- North Eastern Zone: This zone covers the districts of Kancheepuram, Tiruvellore, Vellore, Thiruvannamalai, Cuddalore (excluding Chidambaram and Kattumannarkovil taluks) and Ariyalur and Perambalur taluks in Perambalur district.
- North Western Zone: This zone comprises Dharmapuri district (Excluding hilly areas), Salem and Namakkal districts (Excluding Tiruchengode taluk) and Perambalur taluk of Perambalur district.
- Western Zone: Comprising Erode and Coimbatore districts, Tiruchengode taluk of Namakkal, Karur Taluk of Karur district and northern parts of Madurai district.
- Cauvery Delta Zone: This zone covers the Cauvery Delta area in Thanjavur, Nagapattinam,Thiruvarur districts and Musiri, Tiruchirappalli, Lalgudi, Thuraiyur and Kulithalai taluks of Tiruchirappalli districts, Aranthangi taluk of Pudukottai and Chidambram and Kattumannarkoil taluks of Cuddalore District.
- Southern Zone: This zone includes Ramanathapuram, Virudunagar, Sivaganga, Tuticorin and Tirunelveli districts, Dindigul and Natham taluks of Dindigul district, Melur, Tirumangalam, Madurai South and Madurai North taluks of Madurai district and Pudukottai district (excluding Aranthangi taluk).
- High Rainfall zone: This zone consists of Kanyakumari district.
- Hilly zone: This zone covers the hilly regions, the Nilgiris, Shevroys, Elagiri-Javadhi, Kollimalai, Pachaimalai, Anamalais, Palanis and Podhigai malai.