Kota wet bulb temperature: what the IMD normals say about heat stress

Kota wet bulb temperature is the number that explains why a 32 C day in July can feel more draining than a 41 C afternoon in May. The ordinary thermometer reading, the dry bulb temperature, tells you how hot the air is. The wet bulb temperature tells you how well your body can cool itself by sweating, because it is the lowest temperature a wet surface can reach through evaporation. When the air is dry, the wet bulb is far below the dry bulb and sweat works well. When the air is humid, the two numbers move close together and sweating stops helping.

This guide uses the India Meteorological Department’s (IMD) Climatological Tables 1991-2020 for Kota (station 42452), which list mean wet bulb and dry bulb temperatures at two fixed observation times: 08:30 IST (03 UTC) and 17:30 IST (12 UTC). These are long-term averages, not a forecast. For today’s conditions, see Kota weather today.

Kota wet bulb and dry bulb temperature by month

Month	Dry bulb 08:30	Wet bulb 08:30	Dry bulb 17:30	Wet bulb 17:30	Gap at 17:30
January	13.7 C	10.5 C	21.6 C	14.1 C	7.5
February	17.5 C	12.4 C	25.7 C	15.7 C	10.0
March	23.9 C	15.5 C	32.0 C	17.9 C	14.1
April	30.5 C	18.3 C	37.7 C	19.9 C	17.8
May	34.2 C	22.0 C	41.0 C	22.5 C	18.5
June	32.8 C	24.6 C	38.2 C	24.8 C	13.4
July	29.0 C	25.4 C	32.1 C	25.9 C	6.2
August	27.8 C	25.1 C	30.4 C	25.8 C	4.6
September	28.2 C	24.0 C	32.0 C	24.6 C	7.4
October	26.5 C	19.6 C	32.4 C	20.7 C	11.7
November	21.2 C	15.2 C	27.8 C	17.5 C	10.3
December	15.8 C	11.8 C	23.5 C	15.2 C	8.3
Year	25.2 C	18.7 C	31.3 C	20.4 C	10.9

The gap column is simply the dry bulb minus the wet bulb at 17:30 IST. A big gap means dry air and effective sweating; a small gap means humid air.

Dry heat in May, humid heat in July

Kota’s hottest air comes in May. At 17:30 IST the mean dry bulb is 41.0 C, and IMD’s mean daily maximum for the month is 42.6 C. But the wet bulb at the same hour is only 22.5 C, because afternoon relative humidity averages just 15 percent. In that air, sweat evaporates almost instantly. The danger in May is the sheer heat load, dehydration and heat exhaustion, and the hot westerly loo winds described in our Kota wind guide.

By July the picture reverses. The dry bulb at 17:30 falls to 32.1 C, but the wet bulb rises to 25.9 C, the highest of the year, and the gap shrinks to about 6 degrees. In August it narrows to under 5 degrees. Sweat drips instead of evaporating, clothes stay damp and the body struggles to shed heat even though the thermometer looks moderate. That is why many people in Kota find the humid breaks in the monsoon, when the sun comes out between showers, the most tiring weather of the year. Our Kota humidity guide gives the relative humidity behind these figures.

June sits between the two. Early June is still dry and fierce; once pre-monsoon moisture arrives, wet bulb values climb quickly while temperatures stay high. That combination, high dry bulb and rising wet bulb, is the most stressful mix Kota sees. See Kota weather in June.

How high is too high?

Researchers use wet bulb temperature to describe the limit of human heat tolerance. A widely cited 2010 study by Sherwood and Huber argued that a sustained wet bulb temperature of 35 C would make it impossible for the human body to shed its own heat, even at rest in the shade. A 2022 laboratory study by Vecellio and colleagues found that young, healthy people reached their critical limit at lower values, around 31 C wet bulb in warm, humid conditions, and that a single wet bulb threshold does not work in hot, dry air.

Kota’s long-term means, 25 to 26 C at the peak, are well below those values. That does not make humid heat harmless. The means are averages over many years at two fixed hours, and individual days can be several degrees higher. Heat illness also begins long before any survival limit, especially during heavy work, for people who are not used to the heat, and for older people, young children and those with heart, kidney or lung conditions. Treat the research thresholds as a ceiling, not a target.

Who should pay attention

• Outdoor workers in construction, farming and delivery face the highest risk during humid spells from June to September, when physical work adds a lot of internal heat.
• Students in hostel rooms with poor ventilation feel humid nights badly. Our Kota weather for students guide has practical tips.
• Visitors from drier or cooler places often underestimate monsoon heat because the thermometer reading looks lower than in May.
• Older people and people with health conditions should avoid exertion in the hottest, most humid hours and keep rooms ventilated.

Practical ways to cope with humid heat

1. Drink water steadily, not only when thirsty, and add oral rehydration salts if you are sweating heavily.
2. Move air. A fan helps evaporation in humid weather; open windows at night when the outside air is cooler.
3. Wear loose, light cotton that lets sweat evaporate.
4. Shift effort to the morning. In July the 08:30 wet bulb is 25.4 C, close to the evening value, but the dry bulb is about 3 degrees lower and the sun weaker.
5. Know the signs of heat exhaustion and heatstroke, and act quickly.

For the wider summer picture, read Kota heatwave and Kota weather in July. IMD heat and district warnings are explained in Kota weather warnings.

A note on the data

IMD measures wet bulb temperature with a psychrometer: two thermometers side by side, one with its bulb kept moist by a wet muslin wick. The tables used here are station means for 1991-2020; they are not the same as the Wet Bulb Globe Temperature (WBGT) used in occupational safety, which also accounts for sunshine and wind. Our Kota weather station guide explains what else the observatory measures.