Best Climate for Growing Cotton: Temperature and Rainfall

The best climate for growing cotton is warm and sunny, with a long frost-free season and enough water at the right time. Cotton Australia puts the ideal at days of 27 to 32°C (81 to 90°F) and nights of 16 to 20°C (61 to 68°F). FAO lists a growing period of about 180 to 195 days and a seasonal water need of roughly 700 to 1,300 mm (28 to 51 inches), which can come from rain, irrigation or both.

That makes cotton a crop of warm temperate, subtropical and tropical climates, grown from the US Cotton Belt to Australia and southern Africa. This guide gives the numbers stage by stage, with a heat-unit chart, a water chart and a calculator for a five-day irrigation top-up. For the ground side of the same question, see our guide to soil for growing cotton.

Best climate for growing cotton in one table

Different agencies give slightly different bands because they work in different regions and with different varieties. The table shows what each source says, so you can compare them with your own site.

Treat these as ranges, not promises. A short-season variety, a sandy soil or a windy site shifts the numbers. Ask your state or national cotton extension service for local figures before you plan.

Cotton temperature requirements by growth stage

Cotton grows with heat, so the best way to track it is to count heat units instead of days. Texas A&M’s cotton production guide describes the DD60 system. For each day you take the average of the high and the low in °F and subtract 60. The guide gives 22.5 DD60 for a day with a high of 90°F and a low of 75°F. It sets the base at 60°F, the lowest temperature at which cotton keeps developing, and it treats about 95°F as the upper limit for useful heat.

Chart

Heat units (DD60) needed for each growth stage

DD60 per stage, midpoint of the published range; base 60°F

The guide’s table shows how many heat units each stage needs. Planting to emergence takes 50 to 60 DD60 and 4 to 9 days. Emergence to the first square takes 425 to 475. From the first square to a white flower takes 300 to 350, and a white flower to an open boll takes about 850. Planting to harvest takes about 2,600 DD60 over 130 to 170 days. The National Cotton Council gives the same 50 to 60 DD60 and 4 to 9 days for planting to emergence in the Mid-South.

Here is how the formula works on a few days. The 90°F and 75°F day is the Texas A&M example. The others use the same formula.

A hot, steady week adds 100 to 150 DD60, while a cool week adds almost none. That is why a late, cold spring can set a crop back by weeks even when the calendar looks normal. Keep a running total from planting, compare it with the stage table, and you will know whether first flower is close or still two weeks away. Texas A&M adds that a cotton plant adds a new node every 50 to 60 DD60, whether that takes 2 days or 10, so counting nodes gives a second check on your heat-unit total. Cool nights below 60°F do not subtract heat units that are already counted.

Seed and seedling

Cold soil is the first risk. Cotton Australia says the soil is warm enough once it reaches 14°C at 10 cm depth for at least three days in a row. Cotton SA asks for about 17.5°C in the top 3 cm for ten days. LSU AgCenter looks for a mean daily temperature of 65°F (18.3°C) or more at a 4-inch depth. LSU also says yield potential may drop when fewer than 10 DD60 build up in the five days after planting.

Squares, flowers and bolls

This is the stage where heat hurts most. Mississippi chamber studies, summarised in a University of Arizona Cooperative Extension bulletin (2008), found that fruit retention and yield peaked when the mean temperature was 77 to 82.4°F (25 to 28°C). Retention fell fast above 82.4°F and was close to zero above 91.4°F (33°C) in chamber studies. Arizona’s own field work found that most losses came from bolls dropping 3 to 5 days after bloom.

Pollen is part of the reason. In the same bulletin, pollen germination peaked at 82.4°F and fell sharply above 98.6°F (37°C). Cotton SA names a similar ceiling for its growers: an average above 20°C, but not above 34°C, between flowering and boll growth.

Boll opening and fibre

Temperature also shapes the fibre. The National Cotton Council lists temperature among the factors that set fibre length, strength and maturity. Cotton SA warns that minimums below 15.5°C during boll growth can cut yield and fibre quality, and that the plant is sensitive to early frost. Bolls that mature late in cool weather take longer to finish.

When it gets too hot or too cold

Cotton Australia describes cold shock below 11°C and hot shock above 36°C, both of which slow growth and can delay maturity. It adds that long spells of cloud, or very hot weather during flowering, can lower yield potential. Cotton SA reports that temperatures above 36°C can hurt growth.

The Arizona bulletin separates heat from warm nights. It notes that some researchers blame warm nights alone for poor retention, but says this idea has not been fully tested or verified in Arizona. Its authors cite work concluding that humid monsoon air, not night heat alone, explains the link there. In practice, watch the whole weather picture and not a single number.

Frost is the other limit, and Cotton SA lists early frost as a risk to the crop. If your frost-free season is shorter than the 180 to 195 days FAO lists, ask your local extension service which shorter-season varieties suit your site, and plant once the soil is warm.

How much rain and water cotton needs

Cotton is often called drought tolerant because its taproot can reach more than 1 metre, according to Cotton SA. Even so, it needs steady water to make a full crop. FAO’s indicative table gives 700 to 1,300 mm for the whole season. Cotton SA gives 500 to 650 mm of rain and irrigation together for best yields, and 300 to 400 mm for rainfed land, depending on region, soil and climate.

Chart

Seasonal water for cotton: four different bases

mm per season; bars differ in basis: rain-only supply, rain plus irrigation supply, crop water use, FAO indicative crop need

In the United States, a Cotton Incorporated guide for humid regions puts seasonal water use as high as 40 inches for long-season varieties in the desert Southwest, about 30 inches near Lubbock, Texas, and 18 inches at the low end in the humid Southeast, mostly 20 to 25 inches. A Virginia Tech Extension irrigation workshop presentation (March 2018) lists 23.6 inches at Tifton, Georgia, for May to September in 2009 to 2012, with a range of 18.3 to 32.6 inches.

Timing matters as much as the total. The humid-region guide notes that the humid parts of the Cotton Belt get about 45 to 55 inches of rain a year, almost twice the seasonal water use, yet crops still suffer because rain rarely falls when needed. Peak daily use is about 0.25 to 0.3 inch, or around 2 inches a week, in summer near Columbia, South Carolina.

Which stage needs the most water

Water demand follows the canopy. Texas A&M gives crop coefficients (Kc) for the Texas Northern High Plains. A coefficient of 1.10 at peak bloom means the crop uses 10% more water than the reference value, while a seedling uses only 7%. The chart below plots all eight stages. Multiply your local reference evapotranspiration by the Kc to find the crop’s use.

The Virginia Tech presentation gives a weekly guide of about 0.75 to 1 inch a week before bloom, 1 to 2 inches a week at bloom, and 0.75 inch a week from cutout to first open boll. Dry spells hurt at different stages in different ways, and heat makes them worse. Too much water during flowering and boll growth is also harmful, says Cotton SA, as are irrigation gaps of more than 5 to 7 days that cause squares to shed.

Rain at the wrong time

Dryland cotton needs a full soil moisture profile at planting and rain through summer, says Cotton Australia. It also notes that rain on open bolls can discolour the lint, which is why irrigated cotton in dry regions is easier to protect. Cotton SA lists high air humidity during boll ripening as harmful, and prefers an open canopy where humidity is a problem.

Chart

Cotton crop coefficient (Kc) by growth stage

Kc for the Texas Northern High Plains; crop water use = reference ET x Kc

Which regions fit cotton’s climate

The USDA Economic Research Service says US cotton is grown mainly in 17 southern states of the Cotton Belt, from Virginia to California. It is planted from March to June and harvested from August to December, and Texas supplies about 40% of US production in recent years.

Australia grows both irrigated and rain-grown cotton, and Cotton Australia notes that irrigated cotton is better suited to low-rainfall places because the grower controls moisture. South Africa grows it under irrigation and on rainfed land, with an ideal planting window that Cotton SA places in late October for its conditions.

If your region has a short, cool or wet summer, cotton is a risky choice. Compare your own record with the DD60 totals above: you need about 2,600 DD60 from planting to harvest on the Texas A&M scale. For a wider look at how climate decides what cotton systems work, our page on cotton cultivation covers more regions.

▶ A Farmonaut video on how cotton farming thrives, from climate conditions to the technology growers use. · 9:17

Planting window: wait for warm soil

Calendar dates are only a guide. LSU AgCenter’s cotton specialist says that if cotton is planted too early, seedling survival drops and the plants are less vigorous. LSU adds that delaying planting up to four weeks until conditions are right may change flowering by only one to two weeks. Cotton SA estimates that planting after the first or second week of December in its conditions may cut potential yield by up to 25%.

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Soil temperature agencies use before planting cotton

°C; each rule uses a different depth and time span

Use soil temperature, a five-day forecast and your DD60 count to choose the day. Plant into moisture, not into a cold snap.

Calculator: how much water to replace in five days

Use the Texas A&M method to see how much to apply. Multiply the five-day reference evapotranspiration (PET) by the crop coefficient, subtract useful rain, then divide by your system’s efficiency. Texas A&M’s own example only multiplies and divides; the rain step is our addition. The calculator does this and scales the answer to your field.

Try the numbers for your own farm below.

What to do when your climate is not ideal

You cannot change the weather, but you can shift how the crop meets it. These steps follow what the extension sources above recommend.

• Match planting to soil heat. Use the thresholds above and a five-day forecast, not the calendar.
• Pick a variety for your season length. Cotton SA points out that short- and long-season types change the best planting date. Ask local trial results which heat-unit class fits your site.
• Irrigate to the stage. Aim to keep soil water adequate from early flowering through early boll formation, which Cotton SA names as the important period.
• Keep moisture in the soil. Cotton Australia says most growers now leave stubble standing and mulch it back in, which reduces evaporation.
• Watch humidity at ripening. Use an open canopy and sensible plant populations where humid air is a risk.
• Track fruit retention. Arizona’s bulletin ties fruit retention to heat stress, so count bolls through the bloom period.

Water-saving practices also help whatever the climate. Our guide to efficient water use and our overview of crop management strategies cover the wider options. Follow local rules on water use, and check product labels and local advice before any spray decision.

▶ A Farmonaut video on cotton cultivation challenges, from pests to water management, and how technology helps. · 7:38

Using satellite maps to watch weather stress

Satellites cannot read the weather inside a canopy, but they can show how the crop responds to it. NASA explains that satellite vegetation maps show the density of green plant growth, and the most common measure is the Normalized Difference Vegetation Index (NDVI). NASA also notes that comparing a month’s NDVI with the long-run average for that month gives an anomaly, a way to see where plant cover is behind normal.

For a cotton field, that means a map can show which block is lagging after a hot spell or a dry fortnight. It does not say why. Walk the field to check for water, heat, pests or nutrients. The Farmonaut Satellite + AI Farm Monitoring System provides this kind of vegetation map, and developers can pull weather and field data through the weather API documentation or the satellite API. Farm owners can start from the app page.

Moisture sensors in the field complement this view: see our note on sensors in cotton farming. Disease risk also rises in wet, warm spells, so see our overview of fungal diseases. And for how healthy soils support steady water supply, read about regenerative agriculture.

▶ How satellite NDVI maps show crop stress across a large farm. · 4:09

FAQ

Cotton is a crop of which type of climate?

Cotton suits warm climates with a long season: tropical, subtropical and warm temperate. FAO’s indicative values show about 180 to 195 days of growth. It needs hot, sunny days and enough water, from rain or irrigation.

What temperature does cotton need?

Cotton Australia gives 27 to 32°C by day and 16 to 20°C by night as ideal. Cotton SA asks for an average above 20°C during flowering and boll growth, and says temperatures above 36°C can hurt growth.

How much rainfall does cotton need?

FAO’s indicative range is 700 to 1,300 mm per season. In South African conditions, Cotton SA gives 300 to 400 mm for rainfed cotton and 500 to 650 mm of rain plus irrigation. Cotton SA names early flowering to first boll formation as the period when water matters most.

Can cotton be grown in a cool or wet climate?

It is risky. Cold soil hurts seedlings, boll growth needs heat units, and humid air at ripening harms the crop, according to Cotton SA. Check your DD60 total for the season against the roughly 2,600 DD60 that Texas A&M gives from planting to harvest.

When is the right time to plant cotton?

Plant when the soil is warm enough, not on a fixed date. Cotton Australia uses 14°C at 10 cm depth for three days, and LSU AgCenter looks for 65°F at 4 inches. Local extension services publish dates for your area.

How hot is too hot for cotton?

The University of Arizona reports that fruit retention fell fast above a mean of 82.4°F (28°C) and was close to zero above 91.4°F (33°C) in chamber studies. Field results depend on humidity, variety and irrigation.

Related pages on our site: agribusiness partnerships and when cotton is harvested.