Normally, the northeast monsoon rain is associated with cyclonic formation. In this season, the amount of rainfall decreases from east to west.

The relative humidity in Tamil Nadu is found to be higher when compared to summer. The average humidity of the air is about 68% in the month of May, whereas it is 82% in January.

The northeast monsoon season occurs between october and December. The coastal and interior plains of Tamil Nadu are benefitted by this rainy season. Normally, Northeast Monsoonal rain is highly associated with the cyclonic formation. In this season, amount of rainfall decreases from east to west. Except Kanyakumari, all interior south and western parts of Tamil Nadu receives lesser rainfalls. 

November is the month of cyclonic rainfall in Tamil Nadu.

• Unlike other district in Tamil Nadu, Kanyakumari district  has a rainfall both during the South West and the North East monsoons. 

These Monsoons being the branch of Bay of Bengal Monsoon move westwards along the Himalayas. These monsoon winds on moving away to western part of country gradually lose moisture causing less rainfall. Hence rainfall decreases from west to east. The inflow of the south-west monsoon into India is such that the windward side of the Western Ghats receives very heavy rainfall, more than 250 cm. The rain shadow region receives scanty rainfall and the moisture laden clouds shed the maximum rainfall of this season in the north-eastern part of the country. 

In Tamil Nadu, the northeast monsoon season occurs between October and December. The coastal and interior plains of Tamil Nadu are highly benefitted by this rainy season. 

According to the National Forest Policy, a region should have 33% of its land under forest.

According to the latest enumeration available with the Forest department, despite having excellent irrigation systems, water harvesting structures and annual moderate rainfall, Thanjavur district has the percentage of forest cover is just 1% of the total geographical area. Out of 3396.57 square km geographical area, only 111.87 square km area has vegetation.

In Tamil Nadu there is only 17.5% of the area under forest cover. Tamil Nadu is extremely rich in biodiversity but adequate attention has not been paid in the past to assess it effectively and as a result many species have become endangered. 

Tropical evergreen forests are characterized by heavy rainfall and a warm climate. The commercially important trees grown in this area are ebony, mahogany, rosewood, rubber and cinchona. These forests also have a variety of animals like elephants, monkey, lemur and deer and various birds, bats, sloth, scorpions and snails.

In Tamil Nadu, forests are confined to Western Ghats and hills, where rainfall is generally above 2000 mm. Considering the distribution pattern of certain characteristic species that reflect the climatic variations, especially temperature, the forests are further subdivided into low which is less than 800 m and medium which ranges from 800-1450 m elevation.

Sandalwoods are the scented woods which are heavy, yellow, and fine-grained, and unlike many other aromatic woods. Though the tree of sandalwood can grow under a variety of environmental conditions, the finest heartwood is formed only in dry, rocky and hilly terrain in Tamil Nadu. Major parts of sandalwood are grown in Nilgiris, Coimbatore, Erode, Salem, Dharmapuri, Thiruvannamalai, Vellore, Namakkal and Villupuram Districts, this species naturally spread over in large areas.

• The only rubber growing district in Tamil Nadu is Kanyakumari District. 
  
• In Kanyakumari District 19233  rubber plantation are available which produce 24020 tonnes of rubber annually.
  

Nilgiris in Tamil Nadu possesses the highest percentage of area under forest. It has 8.35% to geographical area according to district-wise forest cover  of Tamil Nadu in 2007.

• A mangrove is a shrub or small tree that grows in coastal saline or brackish water. 

As the name implies tropical evergreen forests are evergreen and they never shed their leaves in a particular season.

• A mangrove is a shrub or small tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves occur worldwide in the tropical and subtropical tidal areas.

The trees of tropical deciduous forests shed their leaves to avoid the loss of moisture during dry season.

Tropical deciduous forests are the most widespread forests of India. They are also called the monsoon forests. Tropical Deciduous Forests thrive where the rainfall is between 100 to 200 cm. The eastern slopes of the Western Ghats have dry as well as moist deciduous forests marked predominantly by Teak, Sal, Shisham, Sandalwood. etc. trees. They are found in the north eastern states of Jharkhand, West Orissa and Chhattisgarh. Moist Deciduous Forests are also found on the eastern slopes of the Western Ghats.

• Pichavaram, near Chidambaram in Cuddalore District, is one of the largest mangrove in India.
• Pichavaram ranks among the one of the most exquisite scenic spot in Tamil Nadu and home of many species of aquatic birds.
  

Tropical Deciduous Forests are the most widespread forests of India. They are also called the monsoon forests. Tropical Deciduous Forests thrive where the rainfall is between 70cm. and 200 cm. The eastern slopes of the Western Ghats have dry as well as moist deciduous forests marked predominantly by Teak, Sal, Shisham, Sandalwood etc. trees. They are found in the north eastern states of Jharkhand, West Orissa and Chhattisgarh. Moist Deciduous Forests are also found on the eastern slopes of the Western Ghats. Teak trees are the most dominant species of trees found in these forests.

• Tropical deciduous forests are also called 'Monsoon forests'. 

The natural vegetation can be broadly divided into five different types. They are:

When the retreating monsoon blows from the northeast across the Bay of Bengal, it picks up a significant amount of moisture, which is subsequently released after moving back onto the peninsula. Thus, from October to December the coast of Tamil Nadu state receives at least half of its roughly 40 inches (1,000 mm) of annual precipitation. That rainy extension of the generally dry retreating monsoon is called the northeast, or winter monsoon.

As the southwest monsoon starts its downpour of rain in the Western Ghats, the western parts of Tamil Nadu receive about 150 cm of rainfall on an average. Most of the eastern and central parts of Tamil Nadu become rainshadow region for this season. This occurs due to the southwesterly direction of monsoonal winds in this season. In general, the amount of rainfall of south west monsoon decreases from west to east.