Humidity

The amount of water vapour in the air, expressed as relative humidity (%) — higher means more moisture and a stickier feel.

basic

What is Humidity?

Humidity measures the amount of water vapour in the air. It is one of the most important weather variables for comfort and health, especially in monsoon-driven climates like South Asia where humidity routinely reaches 80–95% in the rainy season.

Two related but distinct measurements are commonly reported:

Relative Humidity (RH) — expressed as a percentage. It tells you how close the air is to its saturation point at the current temperature. 100% RH means the air can hold no more water vapour and dew or rain may form.
Absolute Humidity — measured in grams of water per cubic metre of air. Less commonly used in everyday weather reports.

The figure shown on Mausam Online is relative humidity, which is what most weather apps display and what people generally mean when they say “humidity.”

Why humidity matters

The human body cools itself primarily through sweat evaporation. When humid air is already saturated with water, sweat evaporates much more slowly, and your body cannot dump heat efficiently. This is why a 32°C day in coastal Mumbai feels far more oppressive than a 38°C day in dry Jaisalmer.

Three temperature concepts capture this:

Heat index — a comfort metric that combines temperature and humidity.
Wet-bulb temperature — the lowest temperature the air can reach by evaporation alone; the upper limit of safe human exposure is ~35°C wet-bulb, beyond which the body cannot cool itself.
Feels-like temperature — what the combination of heat, humidity and wind feels like on your skin (the value Mausam Online displays under each city’s current temperature).

In South Asia’s coastal cities — Mumbai, Chennai, Kolkata, Karachi, Chittagong, Cox’s Bazar — the combination of high temperature and high humidity is now occasionally pushing wet-bulb readings close to lethal thresholds.

Humidity through the year in South Asia

Humidity in South Asia follows a clear seasonal pattern, driven by the monsoon:

Pre-monsoon (March–May): Hot and dry in the northern plains (humidity often 20–40%), more humid on the coast.
Monsoon (June–September): Humidity routinely 80–95% across most of the country. This is when heat and humidity combine to feel most oppressive.
Post-monsoon (October–November): Humidity drops; pleasant transitional weather.
Winter (December–February): Cold and relatively dry in the north (40–60%); coastal areas remain moderately humid.

Regional patterns:

Coastal cities (Mumbai, Chennai, Karachi, Dhaka, Chittagong) — 70–90% RH most of the year.
Indo-Gangetic plain (Delhi, Kanpur, Lucknow, Patna) — wide swings: 20–40% in May, 80%+ in monsoon.
Dry interior (Rajasthan, interior Sindh, Balochistan) — typically 20–40% year-round.
Bay of Bengal coast (Kolkata, Bangladesh) — high humidity all year due to proximity to warm sea.

Health effects of high humidity

Sustained high humidity exposes people to several health risks:

Heatstroke and heat exhaustion — primary cause of monsoon-season mortality among outdoor workers.
Mould and respiratory illness — indoor mould thrives at humidity above 60%.
Dehydration — paradoxically you can become severely dehydrated in humid weather because you sweat more.
Worsening asthma and COPD — humid air contains more allergens and irritants.
Heat rash (“prickly heat”) — common in children during monsoon.

Conversely, very low humidity (below 30%) also causes problems: dry eyes, cracked skin, nosebleeds, increased respiratory infection.

Measuring humidity

A hygrometer is the standard instrument. Modern weather stations use electronic sensors; older designs used a wet-bulb / dry-bulb pair of thermometers (“psychrometer”) and a lookup table. Smart-home humidity sensors are increasingly common.

The data on Mausam Online comes from the Open-Meteo API using readings from major weather model and station networks (ECMWF, GFS), updated hourly.

How to manage humidity

For your body:

Hydrate continuously — water, ORS, nimbu pani, coconut water, buttermilk.
Wear light, breathable cotton clothing.
Schedule outdoor work for early morning or evening.
Avoid alcohol and excessive caffeine in high humidity.

For your home:

Use a dehumidifier indoors, especially in coastal apartments.
Run AC in “dry mode” — lowers humidity without aggressive cooling.
Improve ventilation in kitchens and bathrooms.
Keep silica gel sachets in cupboards to prevent mould on clothes and electronics.

Frequently asked questions

Is 50% humidity high or low? For most South Asian cities, 50% RH is moderate and comfortable. Below 30% it feels dry; above 70% it feels muggy. Indoor 40–50% is generally considered the healthiest range.

Can humidity be 100%? Yes, briefly — usually during heavy rain or thick fog. At 100% RH, the air is fully saturated and any additional moisture condenses immediately into mist, dew or rain.

Why does the same temperature feel different in Delhi vs Mumbai? Humidity. Delhi summer at 42°C and 25% humidity feels hot but tolerable in shade. Mumbai at 32°C and 85% humidity feels much more oppressive because sweat doesn’t evaporate.

What is dew point and how is it different from humidity? Dew point is the temperature to which air must cool before it becomes saturated (100% RH). High dew point (above 25°C) feels uncomfortable regardless of the actual humidity number.

Where can I check humidity for my city? Every city page on Mausam Online shows current humidity alongside temperature and wind: Mumbai, Chennai, Kolkata, Karachi, Dhaka.