Vilathikulam is located in the heart of the Karisal Kaadu region (Karisal meaning "black soiled"). The soil in this area is black and has a clay-like stickiness.
The climate of Karisal Kaadu is semi-arid, with hot and dry summers. Both the temperature and humidity are usually high, being close to the equator and barely 25 kilometres from the shore. The clay-like soil retains moisture well; although crops like paddy and sugarcane can never be grown in this area, many 'punsei' (colloquial Tamil: PUNJAI) crops such as green chili, corn, groundnuts, 'kambu' ([Pearl millet]) and sunflower are grown. Only a few kinds of tree grow in the Vilathikulam region, owing to the dry arid climate - palm trees, umbrella-like thorny trees called "Kuda maram" in Tamil (Kudai=Umbrella, Maram=tree), and thorny bushes.
Vilathikulam is a peaceful little town, on the northern bank of the Vaipar river, which has water flowing only 15 to 25 days per year. But it has major significance as the bridge connecting the Vilathikulam town on the southern side to the Kovilpatti and Tuticorin routes gets submerged completely when the river flows. It is a single lane bridge constructed during the British Era and is about 1.5 km in length. When there are buses or trucks needing to cross, they flash their lights and the other side, the traffic waits. Since the traffic volume is very low, seldom it results in traffic snarls. A double-way bridge has been newly constructed adjacent to the old bridge recently.
As the panacea of water problem a dam has been constructed across Vaipar in 2006.