Knowledge base
Climate
The climate factors that shape agriculture — temperature, rainfall, drought, frost, humidity, and growing-degree days — and how they affect crops.
20 entries · every entry is sourced and dated
Climate effects are strongly regional and interact with crop, soil, and management. Entries describe general principles, not local forecasts or thresholds.
- Climate metric
Aridity Index
The aridity index is a numerical measure of the dryness of a climate, most commonly the ratio of precipitation to potential evapotranspiration. It is used to classify climates from hyper-arid to humid and to delineate drylands.
- Climate factor
Chilling Requirement
Chilling requirement is the amount of cold exposure during winter dormancy that temperate fruit and nut crops need before they can resume normal growth and flower in spring, with insufficient chilling leading to delayed, uneven, or reduced flowering.
- Climate factor
Dew
Dew is water that condenses from the air onto cool surfaces such as leaves and soil, usually overnight, when those surfaces fall below the dew-point temperature. It adds a small amount of moisture but is agriculturally important mainly because the leaf wetness it creates influences plant diseases.
- Climate factor
Drought
Drought is a period of below-normal water availability — from reduced precipitation, higher evaporative demand, or both — that lowers soil moisture and constrains crop growth, forage availability, and water supplies for agriculture.
- Climate factor
El Niño–La Niña
El Niño and La Niña are opposite phases of a recurring ocean-atmosphere pattern in the tropical Pacific, the El Niño-Southern Oscillation, that shifts rainfall and temperature patterns across many world regions on a multi-month to multi-year cycle, with effects that vary substantially by location.
- Climate factor
Evapotranspiration
Evapotranspiration is the combined loss of water from soil and open water surfaces through evaporation and from plant leaves through transpiration, and it is the primary concept used to estimate how much water a crop needs and when to irrigate.
- Climate factor
Frost
Frost occurs when air or plant-surface temperatures fall to or below the freezing point of water, forming ice that can damage sensitive crop tissue; its timing relative to a crop’s growth stage often matters as much as its severity.
- Climate metric
Growing Degree Days
Growing degree days (GDD) is a heat-accumulation metric that sums daily temperature above a crop-specific base threshold over time, used as a proxy for crop developmental progress rather than calendar days alone. Base temperatures and calculation methods are crop- and region-specific rather than universal.
- Climate metric
Growing Season
The growing season is the period within a year when temperature, moisture, and daylight conditions allow crop growth. It is commonly defined by the frost-free period in temperate regions and by rainfall onset and cessation in tropical and dryland climates, and its length shapes which crops and how many cropping cycles are possible.
- Climate factor
Hail
Hail is precipitation in the form of ice pellets or lumps that forms in strong convective thunderstorms and can physically damage crops, bruising or shredding foliage, fruit, and stems within minutes along a localized storm path.
- Climate factor
Heat Stress
Heat stress occurs when temperatures exceed the physiological tolerance of crops or livestock long enough to impair growth, reproduction, or productivity. Tolerance thresholds differ by species, breed or cultivar, and acclimatisation, so effects are assessed relative to the specific organism rather than a single global temperature value.
- Climate factor
Humidity
Humidity describes how much water vapour is present in the air, most often expressed as relative humidity. It shapes how quickly plants lose water through transpiration and strongly influences the risk of many fungal and bacterial crop diseases.
- Climate factor
Monsoon
A monsoon is a seasonal reversal of prevailing winds that brings a pronounced wet season to large parts of South and Southeast Asia, West Africa, and other regions, followed by a markedly drier season, shaping cropping calendars across those areas.
- Climate metric
Photoperiod
Photoperiod is the length of the daily light period, which varies with latitude and season and acts as a reliable environmental signal that many crops use to time flowering and other developmental changes through a response called photoperiodism.
- Climate factor
Rainfall
Rainfall is the primary natural water input for most agricultural systems, and its amount, timing, and reliability — not just its total — largely determine whether crops can be grown without irrigation and how production risk varies from season to season.
- Climate metric
Solar Radiation
Solar radiation is the energy the sun delivers to the Earth’s surface. It powers photosynthesis and evapotranspiration and drives temperature, making it a fundamental input to crop growth and to the water and energy balance of farmland.
- Climate factor
Temperature
Temperature — of air and soil — is a fundamental driver of plant metabolism, governing germination, growth rate, developmental timing, and the geographic and seasonal range over which a given crop can be grown.
- Climate metric
Vapor Pressure Deficit
Vapor pressure deficit (VPD) is the difference between how much water vapour the air currently holds and the maximum it could hold at that temperature. It expresses the drying power of the air and strongly influences plant transpiration and water demand.
- Climate factor
Vernalization
Vernalization is the promotion of flowering by a prolonged period of low, non-freezing temperature. Many winter cereals and biennial crops must experience a spell of cold before they will flower, which aligns their reproduction with the seasons.
- Climate factor
Wind
Wind affects agriculture in multiple ways — raising evaporative demand and evapotranspiration, risking lodging or physical damage to crops, driving wind erosion on exposed soil, and, at extreme speeds, causing direct structural damage to plants and farm infrastructure.