NDA Geography · Climatology, Atmosphere and Weather
Humidity, Condensation, Clouds and Precipitation
Water vapour in the air (humidity) condenses when air is cooled past saturation, forming dew, fog, frost and clouds; when the droplets grow heavy enough they fall as precipitation — rain, snow, sleet or hail.
Why this matters
10 PYQs spanning easy recall and HARD multi-statement traps. The high-value distinctions: condensation forms (dew, fog, frost) vs precipitation forms (rain, snow, sleet, hail); the cloud families by altitude (high/middle/low) and which clouds bring rain (the nimbus family); and relative humidity (a ratio that FALLS as temperature rises). Drill the cloud names — they recur every year.
Concept 1 of 4: Humidity and relative humidity
Warm air can hold more water vapour than cold air. RELATIVE humidity is how full the air is — the actual vapour as a fraction of the most it could hold at that temperature. So if you heat the air without adding water, its capacity grows and the relative humidity FALLS. When relative humidity is high the air is nearly saturated, so sweat evaporates SLOWLY (and you feel sticky).
Definition
- Relative humidity = the ratio of the actual water vapour in the air to the maximum it can hold at that temperature (often a percentage).
- Higher air temperature → LOWER relative humidity (warm air can hold more, so the same vapour fills a smaller fraction).
- When relative humidity is HIGH, the air is near saturation, so LESS water evaporates from the skin (sweat lingers) — high humidity does NOT speed up evaporation.
- Condensation of vapour into water is influenced by the volume of air, the humidity, and the temperature.
Worked example
Three claims: (1) relative humidity is the ratio of actual vapour to the maximum the air can hold at a given temperature; (2) when relative humidity is high, MORE water evaporates from the skin; (3) higher air temperature gives lower relative humidity. Which are correct?
Practice this conceptself-check · 3 quick reps
The same idea in a real exam question:
NDA · Apr 2024 · Q111Moderate
Example 1 · Climatology, Atmosphere and Weather · Humidity, Condensation, Clouds and Precipitation
Which of the following statements regarding humidity is/are correct ?
1. It is a ratio between the actual amount of water vapour present in the atmosphere and the maximum amount it can hold at a given temperature.
2. When the relative humidity is high, more water evaporates from the skin.
3. Higher the air temperature lower the relative humidity of the air.
Select the answer using the code given below :
High humidity SLOWS evaporation
The seductive wrong claim is that high relative humidity makes MORE sweat evaporate. The opposite is true — near-saturated air can absorb little more, so evaporation (and cooling) SLOWS, which is why humid heat feels worse.
Concept 2 of 4: Condensation forms vs precipitation forms
Sort the watery words into two buckets. CONDENSATION is vapour turning to liquid/solid on a surface or in the air without falling: dew, fog, frost (and clouds). PRECIPITATION is water that FALLS from clouds to the ground: rain, snow, sleet, hail. The classic trap is sleet — it FALLS, so it is precipitation, NOT condensation.
Definition
- Condensation (vapour → water/ice, no falling): dew, fog, frost (and cloud).
- Precipitation (water falling to the ground): rain, snow, sleet, hail.
- Sleet = frozen raindrops / refrozen melted snow-water; it forms when a sub-freezing layer overlies a warmer layer — and because it FALLS, it is precipitation, not condensation.
- Snow, sleet and hail are all forms of PRECIPITATION.
Worked example
Which one is NOT a form of condensation: dew, fog, frost, sleet?
Practice this conceptself-check · 3 quick reps
The same idea in a real exam question:
NDA · Apr 2021 · Q131Moderate
Example 2 · Climatology, Atmosphere and Weather · Humidity, Condensation, Clouds and Precipitation
Which one of the following is not a form of condensation ?
Sleet FALLS — so it is precipitation
Sleet looks like it belongs with dew/fog/frost, but it is frozen rain that falls to the ground, making it precipitation. Condensation forms (dew, fog, frost) do not fall.
Sleet definition — sub-freezing layer OVER a warm layer
Sleet forms when a layer of below-freezing air overlies a warm layer near the ground (raindrops refreeze on the way down). Reversing the layer order is the trap.
Concept 3 of 4: Cloud families and rain-bearing clouds
Clouds are named two ways at once — by their ALTITUDE (high / middle / low) and by their FORM (cirrus = wispy, cumulus = heaped, stratus = layered, nimbus = rain-bearing). The 'nimbo-' / '-nimbus' prefix or suffix always means rain. Stratus-family low clouds (stratus, nimbostratus, stratocumulus) are LOW clouds — a common trap calls them 'high'.
Definition
Clouds are classified by altitude (high/middle/low) AND by form:
- Cirrus — high, wispy, ice-crystal clouds (fair weather).
- Cumulus — heaped, cotton-wool clouds.
- Stratus — layered, sheet-like LOW clouds (Stratus, Nimbostratus, Stratocumulus are all LOW clouds, NOT high).
- Nimbus / nimbo- — the rain-bearing family. Nimbostratus gives steady, CONTINUOUS precipitation; Cumulonimbus gives heavy showers/thunderstorms.
| Cloud | Family / altitude | Weather it brings |
|---|---|---|
| Cirrus | High, wispy ice clouds | Fair, no rain |
| Cumulus | Heaped fair-weather cloud | Usually fair; can build up |
| Nimbus (Nimbostratus) | Low, layered rain cloud | Steady CONTINUOUS rain NDA 2018 — Nimbostratus = continuous precipitation; NDA 2021 — nimbus = the rain-bearing cloud. |
| Cumulonimbus | Towering storm cloud | Heavy showers, thunderstorms |
| Stratus / Stratocumulus | LOW clouds (NOT high) | Overcast, drizzle NDA 2024 — Stratus/Nimbostratus/Stratocumulus are LOW clouds, not high. |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
NDA · Sep 2018 · Q100Moderate
Example 3 · Climatology, Atmosphere and Weather · Humidity, Condensation, Clouds and Precipitation
Which one of the following types of cloud is characterized by continuous precipitation?
Stratus family are LOW clouds
A multi-statement trap calls 'Stratus, Nimbostratus and Stratocumulus' HIGH clouds. They are LOW clouds. The high clouds are the cirrus family (cirrus, cirrostratus, cirrocumulus).
Concept 4 of 4: Sleet, cloudburst and inversion of rainfall
Beyond plain rain, the NDA tests a few special precipitation ideas: SLEET (frozen rain from a cold-over-warm air layering), CLOUDBURST (a very heavy downpour over a tiny area in a short time, triggering flash floods), and 'INVERSION of rainfall' — a feature of TEMPERATE (frontal) cyclones where the rain pattern reverses through the passage of the warm and cold fronts.
Definition
- Sleet — frozen raindrops or refrozen melted snow-water; forms when a below-freezing layer overlies a warmer layer near the ground (statement 1 is the correct definition; statement 2 reverses the layering and is wrong).
- Cloudburst (per the IMD) — heavy precipitation in a short time over a small area, generally during the monsoon, triggering flash floods and landslides.
- 'Inversion of rainfall' is associated with temperate (frontal) cyclones — the cyclonic rainfall of the mid-latitudes, where the warm and cold fronts give a characteristic reversed rainfall sequence.
Worked example
Two claims about sleet: (1) sleet is frozen raindrops and refrozen melted snow-water; (2) it forms when a layer of below-freezing air lies UNDER a warm layer. Which are correct?
Practice this conceptself-check · 3 quick reps
The same idea in a real exam question:
NDA · Apr 2025 · Q92Hard
Example 4 · Climatology, Atmosphere and Weather · Humidity, Condensation, Clouds and Precipitation
Which of the following statements with reference to Sleet is/are correct?
1. Sleet is frozen raindrops and refrozen melted snow-water
2. It occurs when a layer of air with the temperature below freezing point overlies a warm layer near the ground surface
Select the answer using the code given below:
Inversion of rainfall = TEMPERATE cyclone
Don't pick orographic, convectional or tropical-cyclonic. 'Inversion of rainfall' is specifically the frontal rainfall pattern of temperate (mid-latitude) cyclones.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (1)
Cloud families and rain-bearing clouds5 rows
| Cloud | Family / altitude | Weather it brings |
|---|---|---|
| Cirrus | High, wispy ice clouds | Fair, no rain |
| Cumulus | Heaped fair-weather cloud | Usually fair; can build up |
| Nimbus (Nimbostratus) | Low, layered rain cloud | Steady CONTINUOUS rain NDA 2018 — Nimbostratus = continuous precipitation; NDA 2021 — nimbus = the rain-bearing cloud. |
| Cumulonimbus | Towering storm cloud | Heavy showers, thunderstorms |
| Stratus / Stratocumulus | LOW clouds (NOT high) | Overcast, drizzle NDA 2024 — Stratus/Nimbostratus/Stratocumulus are LOW clouds, not high. |
Watch out for (5)
- High humidity SLOWS evaporation→ Humidity and relative humidity
- Sleet FALLS — so it is precipitation→ Condensation forms vs precipitation forms
- Sleet definition — sub-freezing layer OVER a warm layer→ Condensation forms vs precipitation forms
- Stratus family are LOW clouds→ Cloud families and rain-bearing clouds
- Inversion of rainfall = TEMPERATE cyclone→ Sleet, cloudburst and inversion of rainfall
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