BharatSangraha

Kongu Nadu · Deccan Inland Plateau

Terrain and eco-zones

Semi-arid, and unusual in the Tamil country for taking rain from both monsoons. The gap admits enough of the south-west monsoon that Coimbatore gets some June-to-September rain where the rest of the Tamil plain gets almost none — but what mostly comes through is wind, at an annual mean of roughly 18 to 22 km/h and much more in the gusts, which is why the annual total still only reaches 600–700 mm and why the wind farms are where they are. The main rain arrives with the north-east monsoon in October and November. Coimbatore's elevation keeps its nights cool for the latitude; Salem and Karur, lower and further from the gap, run four or five degrees hotter and touch 40 °C in May.

Landforms

The gap itself — a 32 km break between the Nilgiri and Anaimalai blocks, floor near 140 mBlack cotton soil over gneiss across the western taluks, red loam and gravel eastwardThe Nilgiri escarpment, climbing 1,500 m in under 20 horizontal kilometres above MettupalayamThe Shevaroy, Kolli, Kalrayan and Pachaimalai hill blocks, isolated forested massifs rising out of the plainThe Velliangiri and Anaimalai foothills on the southern rimThe Cauvery gorge and carbonatite outcrop at Hogenakkal, where the river drops into a slot canyon

Rivers and waters

Cauvery — the northern and eastern boundary rather than an internal river, taking the region's drainageBhavani — the largest tributary here, rising in the Nilgiris and joining the Cauvery at KooduthuraiNoyyal — the Coimbatore river, seasonal, running past Kodumanal to the Cauvery, with a chain of medieval tanks along itAmaravathi — coming off the Anaimalais and meeting the Cauvery at KarurSarabanga, Thirumanimuthar and Vashishta — the Salem-belt streams, dry for most of the yearSiruvani — small, short, and locally famous for the taste of its water

Through the year

SeasonMonthsTypicalWhat it is like
SummerMarch–May24–40 °CHot and glaring on the Salem and Karur plains, milder at Coimbatore. Mangoes come off in Salem and Krishnagiri, groundnut is lifted, and the koozh pot moves to the front of every house.
South-west monsoonJune–September22–34 °CThe wind season. Three months of steady dry gale through the gap, cloud without much rain, cotton drying fast, and turbines turning at their annual peak. Coimbatore is at its most pleasant.
North-east monsoonOctober–December21–31 °CThe real rain, delivered in short heavy evening storms. Tanks fill, the sowing calendar turns, and the hill roads to Yercaud and Kolli Hills get slippery.
WinterJanuary–February19–30 °CCool, dry and clear. Pongal falls in it, with the cattle events of the Kangayam belt, and it is the best month for the hills and the temple festivals.

Best time to visitNovember to February for the plains and the temples, and the same window for the slope, when the ghat road and the rack railway are at their best. April and May are for the hill blocks — Yercaud and Kolli Hills — and for nobody at all on the plain.

The climate, landforms, rivers and seasons of Kongu Nadu, and the best time of year to visit. (4)