How Hot Is the Amazon Rainforest? Temperature & Humidity

Annual mean air temperature across the Amazon rainforest hovers around 25°C (77°F), with most of the basin sitting between 24°C and 28°C year-round, while relative humidity routinely exceeds 80 percent beneath the canopy. Those numbers sound stable, even mild for the tropics, but they mask enormous variation between seasons, between the forest floor and the open sky, and between intact jungle and cleared land. The Amazon’s heat and humidity story is really about layers and shifts, and both are changing faster than they used to.

What the Baseline Numbers Look Like

The Amazon basin spans roughly 5.5 million square kilometers across nine countries, so “the temperature” is never a single number. A comprehensive analysis of historical trends from 1982 to 2015 found that annual mean temperatures over the Amazon are around 25°C, ranging between about 8°C and 28°C, though the extremes occur in limited areas. Temperatures below 20°C show up mainly in the Andes along the basin’s western edge, from Bolivia north through Colombia. The lowland interior, where most of the dense rainforest grows, stays between 24°C and 28°C throughout the year.¹

Humidity is harder to pin to a single figure because it swings with the seasons and with altitude above the forest floor. Inside intact forest, relative humidity near the ground often stays between 80 and 95 percent, even during drier months. Step into a clearing or pasture, and that number can drop sharply. The combination of high temperature and high humidity is what makes the Amazon feel so oppressive to visitors. A 27°C day at 90 percent humidity produces a heat index well above what the thermometer reads, and your sweat barely evaporates.

Wet Season Versus Dry Season

The Amazon does not have a cool season and a warm season in the way that temperate regions do. Instead, it has a wet season and a dry season, and the difference matters more for humidity and rainfall than for raw temperature. During the wet season, moist air originating near the Atlantic surface is pushed inland and converges over the basin, producing heavy rainfall. In the dry season, weaker winds and large-scale atmospheric sinking dry out the middle atmosphere, reducing cloud cover and moisture levels considerably.²

Temperature during the dry months can actually be higher than during the wet months, partly because fewer clouds let more solar radiation reach the ground and partly because the cooling effect of evaporation weakens. The warming trend since 1980 has been more pronounced during these dry months, amplifying what was already the hotter part of the year.³

This seasonal swing also reshapes how the forest interacts with incoming sunlight and carbon. Satellite observations over a decade identified nine distinct regions within the Amazon, each with different timing of peak photosynthesis. Southern and southwestern forests ramp up growth during the wet season, while central-western to northeastern areas actually increase productivity during the dry season, taking advantage of stronger sunlight when the sky clears.⁴

Life Under the Canopy Is Cooler Than You Think

If you have ever walked from open sunlight into a dense forest, you have felt the immediate drop in temperature. In the Amazon, that effect is measurable and substantial. Research from eastern Amazonia showed that the forest canopy buffers monthly mean temperatures by about 2°C and peak daily maximum temperatures by roughly 4.6°C compared to the air above the treetops.⁵ On a day when satellite data says it is 35°C over the canopy, the forest floor might register closer to 30°C. That difference is huge for the insects, amphibians, fungi, and seedlings that live there.

This buffering effect is not fixed. It depends on rainfall, canopy density, tree height, and even the slope of the terrain. Sites with taller trees, denser leaf cover, and more rainfall provide stronger insulation from the heat above. The rainy season enhances this buffering because the canopy is fully leafed out and evaporation is at its peak. During the dry season, when moisture stress thins the leaf cover and the air above dries out, the buffering weakens.⁶ Low, sparse canopies allow the hot, dry air above to mix downward more freely, coupling conditions above the trees with the forest floor and raising fire risk.⁷

The Forest Makes Its Own Weather

One of the most remarkable things about the Amazon is that the forest actively generates a large share of its own rainfall. Trees draw water from the soil through their roots and release it into the air through their leaves. This process, transpiration, pumps enormous volumes of moisture into the atmosphere. That moisture forms clouds and eventually falls again as rain, recycling water inland across the continent. Research estimates that this recycling is so powerful that the forest meaningfully enhances regional precipitation levels.⁸

This matters for understanding humidity because the Amazon’s moisture does not simply arrive from the ocean. A large portion is produced by the forest itself. When you feel the thick, soupy air under the canopy, a good fraction of that water vapor came out of nearby trees within the past few days. Remove the trees and you do not just lose shade; you lose a major humidity source, which in turn reduces rainfall and raises temperatures in a self-reinforcing cycle.

How Deforestation Turns Up the Heat

Cleared land in the Amazon is consistently hotter than forest. When forest is converted to pasture or cropland, the surface reflects and absorbs sunlight differently. Without canopy shade and transpiration, more of the sun’s energy heats the ground directly rather than being used to evaporate water. In southeastern Amazonia, satellite analysis showed that converting forest to crops reduced the amount of energy going into evaporation by about 32 percent and increased the energy going into heating the air. Over the 2000s, land-use transitions in one intensively studied region warmed the land surface temperature by 0.3°C and reduced evaporation by 35 cubic kilometers.⁹

Modeling studies for eastern Amazonia project the same pattern at larger scales: replacing forest with pasture and soybean fields increases surface temperature and decreases both evaporation and rainfall, especially during the dry season.¹⁰ The difference between a forested patch and a nearby clearing can be stark enough that you can feel it walking across the boundary. Pasture sites experience roughly a sixfold increase in vapor pressure deficit compared to intact primary forest, meaning the air is dramatically drier and pulls moisture out of everything it touches, including dead leaves and soil, much faster.¹¹

Under worst-case scenarios combining ongoing deforestation with high greenhouse gas emissions, models suggest the Amazon could shift toward savanna-like conditions in some regions, with dry seasons lengthening by roughly two months and temperature anomalies in the central Amazon reaching as high as 14°C above current forested baselines. That would push actual maximum temperatures past 46°C in areas that currently peak in the low 30s.¹² A tipping-point analysis suggested that exceeding about 40 percent total deforested area, or 3 to 4°C of global warming, could push the forest past a point of no return toward permanent degradation.¹³

The Warming Trend and El Niño Shocks

The Amazon has been warming at about 0.2 to 0.3°C per decade since the early 1980s, broadly in line with the global average.¹ A more recent analysis covering 1981 through 2023 put the annual mean rate at 0.21°C per decade, adding up to about 0.9°C of warming over 43 years. But extremes have been climbing faster. The hottest 5 percent of temperature readings increased at 0.30°C per decade, and the maximum temperature extremes during the driest period rose at 0.49°C per decade, more than double the average trend. Over those same 43 years, peak dry-season temperatures climbed by roughly 2.1°C.¹⁴

El Niño years punch through these trends like spikes on a graph. During El Niño, the Amazon gets hotter and drier than usual because shifts in Pacific Ocean temperatures suppress the moisture flow into the basin. The 2015–2016 El Niño, combined with the long-term warming trend, produced unprecedented heat and a larger extent of extreme drought than earlier strong El Niño events in 1982–83 and 1997–98.¹⁵ The 2023 El Niño hit similarly hard: air temperatures in the central Amazon during the 2023 dry season ran about 3°C higher than the same period in 2022, and forest understory temperatures at monitoring sites in eastern Amazonia shifted upward by 0.7 to 1.6°C, setting record highs.¹⁶⁵

What makes each successive El Niño more dangerous is that it rides on top of an already warmer baseline. The record-breaking event is not just a temporary spike; it previews where ordinary conditions may head in a few decades.

Rising Atmospheric Dryness and Fire Risk

Temperature alone does not capture the full heat picture. Vapor pressure deficit, or how aggressively the air pulls moisture from surfaces, matters as much as raw temperature for fire risk and plant stress. Over the southern Amazon’s dry season, extreme VPD conditions have been rising rapidly, especially over forested areas. Under a scenario close to current emissions trajectories, climate models project that dry-season VPD intensities will reach 7 to 15 standard deviations above historical norms by century’s end.¹⁷ Numbers that far outside normal would represent conditions unlike anything the current forest has experienced, substantially increasing wildfire risk even in areas that have never burned in recorded history.

What the Heat Means for People

About 30 million people live in the Amazon basin, and for those working outdoors, the combination of heat and humidity already pushes the body’s cooling systems. A physiological modeling study found that the Amazon is among the global regions with the lowest capacity for sustained physical work in heat, averaging around 4 METs (roughly equivalent to brisk walking) as a maximum safe exertion level during the hottest conditions.¹⁸ Outdoor laborers, including farmers, loggers, and miners, routinely encounter heat-stress conditions that medical guidelines classify as dangerous.

Deforestation makes this worse. Modeling that simulated large-scale forest removal found that in-shade wet-bulb globe temperature (a standard heat-stress metric that accounts for humidity, wind, and radiation) exceeded the extreme-risk threshold of 34°C across a large majority of the Amazon basin in the hottest month. In the most aggressive deforestation-plus-warming scenario, WBGT reached 41°C in shade, and outdoor values hit 46°C. Crucially, these extreme values did not appear in scenarios where the forest remained intact, even under the same greenhouse gas assumptions.¹⁹

Urban areas in the basin already demonstrate the effect. In Manaus, a city of over two million people in the central Amazon, the urban heat island effect raises nighttime temperatures about 4°C above surrounding rural forest. The heat index in the urban core reaches about 34°C at night compared to 28°C in the forested rural area nearby.²⁰ Nighttime heat is particularly important for health because it prevents the body from recovering during sleep, compounding the stress of daytime exposure.

Trees Approaching Their Thermal Limits

The Amazon’s trees are adapted to heat, but their tolerance is not infinite. At the transition zone between dense forest and the drier cerrado (savanna), researchers measured actual leaf temperatures and compared them against the temperature at which half the photosynthetic apparatus fails. For several species growing in savanna settings, maximum leaf temperatures already exceed that damage threshold. With a 2.5°C increase in air temperature, the vast majority of studied species showed negative safety margins, meaning their leaves would regularly experience temperatures hot enough to damage the cellular machinery they use to convert sunlight into energy.²¹

Some trees can adjust. A study examining species across a natural temperature gradient in the Amazon found that individuals at warmer sites did shift their thermal tolerance upward. But the adjustment was generally insufficient to maintain the same safety margin. In other words, the trees acclimated a little but not enough to keep pace with rising temperatures.²² Leaf health remained broadly consistent for now, but the shrinking margin leaves less room for error when the next drought or El Niño pushes temperatures further.

Have Amazon Trees Survived This Kind of Heat Before?

Tropical rainforest has persisted in South America for at least 55 million years, spanning periods when global temperatures were considerably higher than today. A phylogenetic analysis of 12 widespread Amazon tree species found that 9 had lineages predating the Pliocene (older than 2.6 million years), and 7 dated to the Miocene (older than 5.6 million years). During the Pliocene, Amazon air temperatures were similar to what low-emission scenarios project for 2100, and during the late Miocene they were similar to high-emission projections. The survival of these lineages suggests these species have passed through warmth comparable to near-term forecasts.²³

That is a comforting data point, but it comes with a caveat. During those ancient warm periods, the Amazon was not simultaneously contending with deforestation, habitat fragmentation, fire intrusion, and a rate of warming far faster than geological norms. The Paleocene-Eocene Thermal Maximum about 56 million years ago pushed tropical sea surface temperatures above 36°C and stressed marine plankton near physiological limits.²⁴ That same event reduced the total number of precipitation events over the Amazon region by up to 30 percent while shifting the remaining rainfall toward more extreme episodes.²⁵ The forest survived, but conditions were harsh enough to leave a mark in the geological record, and the rate of change then played out over thousands of years, not decades.