Basics
- Period: November to mid-March
- Fact: January is the coldest month as the apparent path of the sun is south of the equator.
- Characteristics: Clear skies, pleasant weather, cool and slow north-east trade winds, low temperature, low humidity, wide temperature range.
Temperature in Winter Season
- The 20°C isotherm runs roughly parallel to the Tropic of Cancer.
- Coastal states like Kerala experience moderate temperatures of around 30 degrees and the interior of plains have 22 degrees.
- The Dras Valley in Kashmir is India’s coldest location. In 1908, the lowest temperature recorded at Dras was – 45°C.
Pressure in the Winter Season
- High air pressure over large parts of north-west India due to low temperature coupled with divergence of air resulting in the offshore winds.
- The wind starts blowing from a high-pressure area in the northwest to a low-pressure area in the southeast.
- The wind velocity is low due to a low-pressure gradient.
Western Disturbances in Winter Season
- They become more intense in Rajasthan, Punjab, and Haryana.
- They migrate eastward through the sub-Himalayan belt, eventually reaching Arunachal Pradesh.
- In the Indus Ganga plains, they cause light rain, while in the Himalayan belt, they cause snowfall.
- Following the disturbance’s passage, widespread fog and cold waves set in, lowering the minimum temperature by 5° to 10°C below normal.
- Fog reduces visibility and makes transportation extremely inconvenient.
- The rain caused by western disturbances is good for rabi crops like mustard.
Precipitation in Winter Season
- While crossing the Bay of Bengal, the retreating winter monsoons pick up moisture and cause winter rainfall in Tamil Nadu, south Andhra Pradesh, south-east Karnataka, and south-east Kerala (Usually in the first weeks of November).
- Between October and December, the highest seasonal rainfall occurs.
- The majority of it occurs along Tamil Nadu’s south-eastern coast and adjacent areas of Andhra Pradesh. Following that, it gradually decreases.
- In northwest India, the western disturbances also bring a little rain.
- From the north and north-west to the east, the amount of rainfall gradually decreases.