Reading the climate of ten cities

India is huge, so its climate is not the same everywhere. Table 3.3 gives the average temperature and rainfall for every month at ten stations, from Thiruvananthapuram in the far south to Leh high in the north. In this lesson you learn to read that table like a geographer.

First, turn the numbers into a picture. A climate graph (Fig. 3.14 shows Delhi) puts the 12 months along the bottom. The temperature is drawn as a line, and the rainfall as bars. One look tells you when a place is hot, cold, wet or dry.

Tool 1: distance from the equator (latitude). The lower the latitude, the closer to the equator. In order, from closest to farthest:

• Thiruvananthapuram (8°29'N), Bengaluru (12°58'N), Chennai (13°4'N), Mumbai (19°N), Nagpur (21°9'N), Kolkata (22°34'N), Shillong (24°34'N), Jodhpur (26°18'N), Delhi (29°N), Leh (34°N).

Tool 2: the annual range of temperature. Range = hottest month minus coldest month. A big range means an extreme climate (very hot summers, very cold winters). A small range means an equable climate: about the same all year.

• Leh: from –8.5°C to 17.2°C, a range of 25.7°C: very extreme.
• Thiruvananthapuram: from 26.2°C to 28.7°C, a range of only 2.5°C: equable. It is close to the equator and right on the coast, where the sea keeps it steady.

Tool 3: which months are wet. Most stations get their rain from June to September, from the south-west monsoon. A station that is wet in October and November is getting rain from the retreating (north-east) monsoon.

Tool 4: height and shape of the land (relief). When moist winds hit hills, they are forced to rise, they cool, and they drop their rain. So a hill station can be much wetter than a plain nearby. Shillong stands at 1,461 m in the Meghalaya hills.

Tool 5: what is behind the mountains. Leh lies high up, at 3,506 m, behind the Himalaya. The monsoon winds hardly reach it, so it gets only 8.5 cm of rain in a whole year, spread thinly over most months.

Watch out: do not add up the monthly temperatures to compare places; compare the range (hottest minus coldest). And when you add up rainfall, check that your total matches the 'Annual Rainfall' column.

"With all these differences, is there anything common?" Yes. Look at almost every station: a dry spell, heat building up to May or June, then the rains, then the retreat. The monsoon's rhythm runs through the whole country. That is why the book says the monsoon gives India its climatic unity.

Climate even shapes how people live. Collect pictures of houses and clothes from different parts of India: thick walls against desert heat, sloping roofs where rain is heavy, woollens in the cold mountains.