Mango showers

Geography glossary

Topic: Climate of India and the Monsoon · NCERT: Class 11, Ch 4 "Climate"

Meaning

Mango showers are short pre-monsoon thundershowers that fall in Kerala and coastal Karnataka near the end of summer (April–May). They are named "mango showers" because they help mangoes ripen early.

They matter for two reasons. They are a local feature of India's hot weather season (March to May). They also show how the sea keeps the south-west coast wet and mild while north-west India is dry and very hot.

Explanation

How they form (cause → process → result)

  • Cause: moist air plus strong heat
  • Kerala and coastal Karnataka lie next to the sea, so the air above them holds a lot of moisture.

  • In April and May the sun heats the land strongly during the day.

  • Process: convection

  • The hot ground warms the moist air above it, and this warm air rises fast. This is convection (warm air rising).

  • The rising air cools. Its water vapour condenses, and tall thunderclouds form.

  • Result: thundershowers

  • The clouds break as short, local thundershowers, often with thunder and lightning.
  • These are not the main monsoon rains. They come before the south-west monsoon arrives.

Where they fit in the hot weather season

  • Hot weather season (summer or pre-monsoon season): the time between the cold winter and the arrival of the south-west monsoon. It runs from March to May.
  • The heat belt moves north:
  • After the spring equinox (21 March), the sun seems to move north towards the Tropic of Cancer (23.5°N). This is its apparent northward march. The Earth's tilt causes it.

  • So the hottest zone shifts from the Deccan Plateau (March, about 38°C) to Gujarat and Madhya Pradesh (April, 38–43°C). It then reaches north-west India (May, about 48°C).

  • A thermal low forms over the north (an area of low pressure caused by heating). It stretches from the Thar Desert to the Chota Nagpur Plateau.

  • South-westerly winds blow along the west coast towards this low. They carry moist sea air onto the Kerala–Karnataka coast, and this air feeds the mango showers.
  • Local storms form where air masses meet: at the edges of the trough, moist sea air meets hot, dry land air. The hot ground makes the air rise fast, and local storms break.

Conditions they need

  • Nearness to the sea: this gives moist air. The maritime influence (the sea warms and cools slowly, so it keeps the land's temperature steady) also keeps South India at 26–32°C.
  • Strong daytime heating: this makes the air rise.
  • Warm, humid nights: on the coasts, the minimum temperature rarely falls below 26°C.
  • Nearness to the equator: summer and winter days are not very different here, so the coast stays warm and moist.

Where it occurs

  • Kerala: along the coast of the south-west.
  • Coastal Karnataka: the coastal strip of Karnataka along the Arabian Sea.
  • The wider setting, the south-west coast of India:
  • South India stays at 26–32°C in the hot season.
  • The Western Ghats hills stay below 25°C, because air gets cooler with height.

  • On these coasts, isotherms (lines on a map joining places with the same temperature) run parallel to the coast. Temperature rises from the coast towards the interior.

  • Pre-monsoon showers in other parts of India go by other names:

  • Blossom showers fall in Kerala and nearby Karnataka.

  • Nor'westers strike in Bengal and Assam, where they are called Kalbaisakhi and Bardoisila.

  • "Mango showers" is an Indian local name. It is not a general world climate term.

Don't confuse with

  • Blossom (cherry/coffee) showers: these fall in the same region, Kerala and nearby Karnataka. But they make coffee plants flower. Mango showers help mangoes ripen. Swapping the crop is the most common trap.
  • Nor'westers (Kalbaisakhi in Bengal, Bardoisila in Assam): these are violent evening thunderstorms in the east and north-east from March to May. They bring hail and squalls, and they help tea, jute and rice. Mango showers are milder and fall on the south-west coast.
  • Loo: this is a hot, dry, dusty wind of the northern plains in May–June, strongest between Delhi and Patna. It brings no rain and causes heatstroke. Mango showers bring rain.
  • South-west monsoon rains: these are the main seasonal rains brought by the strong inflow of south-west winds by mid-June. Mango showers are pre-monsoon, so they come before them.

Prelims Hooks

  • Mango showers = Kerala and coastal Karnataka. They help mangoes ripen early.
  • Blossom/cherry showers = Kerala and nearby Karnataka. They make coffee flower. Do not swap the crop.
  • Mango showers fall at the end of summer (April–May). They are pre-monsoon thundershowers, not monsoon rain.
  • Match the storms to their regions: Loo belongs to the northern plains (hot and dry), Nor'westers to Bengal and Assam, and Mango showers to the south-west coast.
  • Kalbaisakhi = West Bengal; Bardoisila = Assam. Both are names for nor'westers, not for mango showers.
  • In the hot season, South India stays at 26–32°C because of the sea, its nearness to the equator and sea breezes. This is why the south-west coast gets showers while the north-west gets the Loo.

Mains Points

  • Regional contrast in one season (GS-I):
  • The north-west is dry and scorching, with the Loo, dust storms and temperatures up to about 48°C.
  • The east is stormy, with nor'westers.
  • The south-west coast is mild and showery, with mango and blossom showers.

  • Together these show how distance from the sea, latitude and the meeting of moist and dry air control India's climate.

  • Hot season sets up the monsoon (GS-I):

  • Strong heating of the north creates a thermal low and pulls the ITCZ northward. The ITCZ (Inter Tropical Convergence Zone) is the low-pressure belt where the trade winds of the two hemispheres meet.
  • This low draws in south-westerly winds along the west coast. The Coriolis force (a turning force from the Earth's spin) bends these winds.

  • Moist air reaching Kerala and Karnataka first gives local mango showers. The full monsoon rains follow by mid-June.

  • Local showers as a farm resource (GS-I/III):

  • Pre-monsoon showers help crops at key stages. Mango showers help mangoes ripen. Blossom showers help coffee flower in Kodagu, Chikkamagaluru, Hassan and Wayanad.
  • The timing of these showers therefore affects farm output on the south-west coast.

Related concepts

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Sources

  1. 1Class 11, Ch 4 "Climate" (primary)