The period October to December is referred to as Northeast Monsoon season
over peninsular India. Earlier this period was also referred to as
"Post-Monsoon Season" or "Retreating southwest Monsoon
Northeast Monsoon season is the major period of rainfall activity over south
peninsula, particularly in the eastern half comprising of the meteorological
subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamilnadu-Pondicherry.
For Tamilnadu this is the main rainy season accounting for about 48% of the
annual rainfall. Coastal districts of the State get nearly 60% of the
annual rainfall and the interior districts get about 40-50% of the annual
Though the principal rainy season for Interior Karnataka, Kerala and
Lakshadweep is the Southwest Monsoon season, rainfall continues till December in
these sub-divisions, the period October-December (Northeast Monsoon )
contributing about 20 % of the annual total.
The increase in rainfall activity over Andhra-Tamilnadu coasts which takes place
sometime around middle of October is generally considered as the "setting
in of Northeast Monsoon". Normal date of onset of the northeast monsoon is
around 20 October with a deviation of about a week on either side.
The rainfall over south peninsula towards the end of southwest monsoon season is mainly in the interior districts
and it generally occurs in the afternoon , evening or early part of the night.
As the season advances the rainfall is mainly in the coastal districts with
the interior districts getting less rain. It generally occurs during night
and early morning hours . Maximum rainfall mostly occurs between 2100 and
0300 hrs IST. Along the east coast rainfall during late night and morning
hours (2400 to 0900 hrs) is an usual feature of northeast monsoon. When
there is a low, depression or cyclone close by the rainfall occurs throughout
Northeast monsoon rains occur in spells of about 3 to 4 days duration. Spells
exceeding 4 days are much less (20%). There are at times long spells of dry
weather with little or no rain.