Rwanda Climate – September 2026 Update

Novarupta (Katmai) eruption

The largest volcanic eruption anywhere in the world in the 20th century - 13 km3 of magma, about thirty times the 1980 Mount St. Helens eruption - at Novarupta in Alaska on 6-8 June 1912. Ash reached 100,000 ft and cooled the Northern Hemisphere by roughly 0.3°C over 1912-13. Unlike a tropical eruption such as Pinatubo, a high-latitude eruption's haze stays in its own hemisphere, so it did little to the Southern Hemisphere.

Smithsonian Global Volcanism Program, Alaska Volcano Observatory, National Park Service, Oman et al. 2005

Post-WWII industrial expansion begins

After the Second World War, coal and oil use grew rapidly across Europe, North America and the Soviet Union. Global sulphur dioxide emissions rose from about 30 to about 130 million tonnes a year by 1980, and the sulphate haze they formed masked part of the greenhouse warming underneath - the effect known as 'global dimming'.

Klimont et al. 2013

How much ENSO really controls Rwanda's climate

ENSO matters in Rwanda, most of all in July-September: the El Niño-La Niña cycle explains about 20% of the year-to-year swing in Rwanda's July-September rainfall, with El Niño years tending drier and La Niña years wetter. That puts Rwanda among the 88 countries in this site's data where ENSO's influence is strong enough to be worth reporting.

NOAA CPC

The 1955-56 La Niña

Rwanda's rainfall for July-September 1955 ran +56% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -1.6°C · RONI -1.4°C

NOAA CPCENSO Tracker

Keeling Curve begins

Charles David Keeling begins continuous measurements of atmospheric CO₂ at Mauna Loa Observatory in Hawaii, starting at about 315 ppm. The record has risen every year since and is now the longest unbroken direct measurement of CO₂ anywhere - the 'Keeling Curve'.

NOAA GMLGreenhouse Gases

Agung eruption

Agung's eruption in Bali put a veil of sulphate haze into the stratosphere that cooled global temperature by about 0.3°C over 1963-66.

Smithsonian Global Volcanism Program, NOAA Global Monitoring Laboratory

The 1972-73 El Niño

Rwanda's rainfall for July-September 1972 ran -17% against its 1961-90 average - the dry July-September that El Niño usually brings here.

ONI +1.8°C · RONI +2.0°C

NOAA CPCENSO Tracker

The 1973-74 La Niña

Rwanda's rainfall for July-September 1973 ran +36% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -2.0°C · RONI -1.9°C

NOAA CPCENSO Tracker

The 1975-76 La Niña

Rwanda's rainfall for July-September 1975 ran +50% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -1.6°C · RONI -1.1°C

NOAA CPCENSO Tracker

Pacific Decadal Oscillation flips to a warm phase

The Pacific Decadal Oscillation - a slow natural cycle in North Pacific sea temperatures - switches from its cool to its warm phase in 1976-77. The change was abrupt enough to be called the 1976-77 Pacific Climate Shift: it warmed Alaska and the west coast of North America, and reorganised North Pacific fisheries.

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Global SO2 emissions peak

Global sulphur dioxide emissions peak at about 130 million tonnes a year, then begin a long decline as Europe, North America and Japan clean up their air. As the aerosol mask thins, the rate of global warming picks up through the 1980s.

Klimont et al. 2013

El Chichón eruption

A sulphur-rich eruption in Mexico whose aerosol cloud stayed in the stratosphere for more than two years, cooling the Northern Hemisphere by about 0.2°C.

Smithsonian Global Volcanism Program

1982-83 El Niño

The strongest El Niño since 1950 on NOAA's Relative Oceanic Niño Index, which strips out the background warming of the tropical oceans before ranking events. On the older index that leaves that warming in, 2015-16 comes out on top instead.

ONI +2.1°C · RONI +2.4°C

NOAA CPC, NOAA CPC (2)ENSO Tracker

The Antarctic ozone hole is discovered

British Antarctic Survey scientists Joe Farman, Brian Gardiner and Jon Shanklin publish their Halley and Faraday measurements on 16 May 1985, showing October ozone over Antarctica had fallen to about two-thirds of earlier decades. The cause is traced to chlorofluorocarbons, and the finding triggers the fastest international environmental response on record.

Nature, UKRI

The Montreal Protocol

Signed in 1987 to phase out ozone-depleting chlorofluorocarbons, the Montreal Protocol turned out to be one of the most consequential climate treaties ever agreed. CFCs are potent greenhouse gases in their own right, and NOAA estimates the Protocol prevented up to 2°C of warming by 2100 - around 1°C from the emissions avoided, and up to 1°C more by sparing forests and other carbon sinks from increased ultraviolet radiation.

NOAA, Wikipedia

CO₂ crosses 350 ppm

Atmospheric CO₂ passes 350 ppm. In the same year James Hansen told a US Senate committee that global warming was already detectable, the moment it entered mainstream politics. Twenty years later, in 2008, Hansen proposed 350 ppm as the safe upper limit - a level the world had already left behind.

NOAA GMLGreenhouse Gases

The 1988-89 La Niña

Rwanda's rainfall for July-September 1988 ran +77% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -1.9°C · RONI -1.9°C

NOAA CPCENSO Tracker

Daytime warming catches up with the night-led pattern

Across 1961-90, 81% of the world's land saw nights warming faster than days. Across 1991-2020 the pattern reversed: 70% saw days warming faster, as the industrial haze that had been dimming daytime sunshine was cleaned up. The study compares two fixed thirty-year windows; measured as a turning point, this site's own global series turns around 1982.

Zhong et al. 2023

Mount Pinatubo erupts

Pinatubo's cooling does not show in Rwanda's own record: 1992, the year after the June 1991 eruption, was an unremarkable year there, 41st-coldest of 76. A single large eruption can hold temperatures down for two or three years; it cannot reverse the trend.

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Atlantic Multidecadal Oscillation flips to a warm phase

The Atlantic Multidecadal Oscillation - a slow natural cycle in North Atlantic sea temperatures, roughly 60-70 years long - flips to its warm phase in 1995. Warm phases are linked to more active Atlantic hurricane seasons, wetter summers in parts of north-west Europe and more frequent drought in the central and western United States.

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1997-98 El Niño

Rwanda's rainfall for July-September 1997 ran -38% against its 1961-90 average - the dry July-September that El Niño usually brings here. It is often treated as the textbook strong El Niño.

ONI +2.4°C · RONI +2.3°C

NOAA CPC, NOAA NCEIENSO Tracker

The 1999-2001 La Niña

Rwanda's rainfall for July-September 1999 ran +18% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -1.5°C · RONI -1.6°C

NOAA CPC ONI

Pacific Decadal Oscillation flips back to a cool phase

The Pacific Decadal Oscillation - a slow natural cycle in North Pacific sea temperatures - flips back to its cool phase around 1998-99. The cool phase that followed is one reason global surface warming appeared to slow in the 2000s, as more heat went into the deep Pacific.

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The 2007-08 La Niña

Rwanda's rainfall for July-September 2007 ran +57% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -1.8°C · RONI -1.7°C

NOAA CPCENSO Tracker

2009-10 El Niño

Rwanda's rainfall for July-September 2009 ran -40% against its 1961-90 average - the dry July-September that El Niño usually brings here. 2010 is also Rwanda's 10th-warmest year in this site's 1950-2025 record.

ONI +1.5°C · RONI +1.5°C

NOAA/IRI ENSO archiveENSO Tracker

Global heatwave days sharply accelerate

Rwanda's own heatwave days - days in warm spells well above the local norm - rose from a 1961-90 average of 0.3 a year to 23.0 in 2016-25. Worldwide, heatwave days have roughly doubled each decade since 2010, as the whole temperature distribution has shifted upwards.

Learn more →Heatwave Days

The 2010-2012 La Niña

Rwanda's rainfall for July-September 2010 ran +28% against its 1961-90 average - the wet July-September that La Niña usually brings here.

ONI -1.6°C · RONI -1.6°C

NOAA CPC ONI

CO₂ crosses 400 ppm

Atmospheric CO₂ passes 400 ppm at Mauna Loa on 9 May 2013 - a level the planet had not seen for 3-5 million years, since the Pliocene, when sea levels were many metres higher.

NOAA GMLGreenhouse Gases

2015-16 El Niño

Rwanda's rainfall for July-September 2015 ran -48% against its 1961-90 average - the dry July-September that El Niño usually brings here. By the raw ONI index it was the strongest El Niño ever measured - a reminder that a strong index does not guarantee a strong local outcome.

ONI +2.6°C · RONI +2.3°C

NOAA CPCENSO Tracker

2015-2025: the eleven warmest years on record

Globally, the eleven warmest years on record have all happened since 2015. Rwanda tracks that closely - ten of its own eleven warmest fall in the same span, with only 2010 outside. Its warmest year is 2024.

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COVID-19 lockdowns - CO₂ emissions dip

Global fossil CO₂ emissions fell about 5.8% in 2020, from 37.0 to 34.8 billion tonnes, yet atmospheric CO₂ still rose 2.5 ppm - the dip barely registers in the atmospheric record. Emissions were back to pre-pandemic levels by 2022.

Le Quéré et al. 2020

Low-sulphur shipping fuel rule (IMO 2020)

New international shipping rules cut the sulphur allowed in ship fuel from 3.5% to 0.5% almost overnight, removing about 8 million tonnes of sulphur dioxide a year. With less sulphate haze over the oceans, it may have added around 0.1°C of warming by 2023-24.

Gettelman et al. 2024

The 2020-2023 'triple-dip' La Niña

Rwanda's rainfall for July-September 2020 ran -39% against its 1961-90 average - the opposite of the wet July-September La Niña usually brings here.

ONI -1.1°C · RONI -1.5°C

WMO, WMO (2)ENSO Tracker

2023-24 El Niño

Rwanda's rainfall for July-September 2023 ran -61% against its 1961-90 average - the dry July-September that El Niño usually brings here. Globally it helped produce the record temperatures of 2023 and 2024.

ONI +2.0°C · RONI +1.4°C

NOAA CPCENSO Tracker

Rwanda's May floods, 2023

On 2-3 May 2023 torrential rain brought flash floods and landslides to western and northern Rwanda, worst in Rubavu, Ngororero, Nyabihu, Rutsiro and Karongi. 131 people died and more than 5,000 houses were destroyed - one of the deadliest disasters in the country's recent history.

ReliefWeb, FloodList