Dar es Salaam — FOR a country thousands of kilometres away from the Pacific Ocean, Tanzania may appear to have little reason to worry about changes taking place in its tropical waters.
But the warming of those distant waters can influence winds, atmospheric circulation and rainfall patterns far beyond the Pacific, including in East Africa.
This is the phenomenon known as El Niño, and Tanzania is now preparing for its possible effects as the country approaches the October-December autumn rainfall season.
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The latest global assessments indicate that El Niño has firmly developed and is expected to strengthen further towards the end of 2026, potentially becoming a very strong event.
For Tanzania, the implications are already being closely monitored by the Tanzania Meteorological Authority (TMA), which has forecast above-normal to normal rainfall in several parts of the country during the autumn season.
Speaking on a different occasion, TMA Director General Dr Ladislaus Chang’a said the phenomenon begins with changes in the Pacific Ocean but can influence weather conditions in many parts of the world.
“El Niño is a weather system associated with an increase in ocean temperatures, particularly in the Pacific Ocean, where, every three to seven years or so, there is a recurrence of ocean temperatures rising above normal,” Dr Chang’a explained.
“As this increase in ocean temperatures occurs in the Pacific region, it is often accompanied by changes in weather conditions in different parts of the world.”
For East Africa, he said, one of the most common consequences is increased rainfall.
“In our part of East Africa, when El Niño occurs, it is often accompanied by increased rainfall or above-normal rainfall in many parts of East Africa,” he said.
It is a relationship that may sound surprising to the ordinary Tanzanian.
How can warmer water in the Pacific affect a farmer in Kagera, a resident of Dar es Salaam or a livestock keeper in Manyara? The answer lies in the intimate connection between the world’s oceans and atmosphere.
The science behind El Niño
El Niño is the warm phase of a larger climate pattern called the El Niño-Southern Oscillation (ENSO).
Under normal conditions, trade winds blow from east to west across the tropical Pacific.
These winds push warm surface water towards the western Pacific, while colder water rises from deeper layers in the eastern Pacific.
During El Niño, that pattern changes, the trade winds weaken, allowing warm surface water to move eastwards.
At the same time, the usual upwelling of cold water in the eastern Pacific is reduced. Sea-surface temperatures consequently become unusually warm across the central and eastern tropical Pacific.
But the significance of this warming goes beyond the ocean, the warmer water changes atmospheric pressure, cloud formation, winds and the distribution of rainfall
These atmospheric changes can then influence weather patterns in distant regions. According to the World Meteorological Organisation (WMO), El Niño is a naturally occurring climate phenomenon that normally develops every two to seven years and typically lasts between nine and 12 months.
Its effects can be felt around the world, although the nature and intensity of those effects differ from one region to another.
This explains why meteorologists in Tanzania monitor conditions in an ocean more than 10,000 kilometres away.
What does El Niño mean for Tanzania?
They are not simply watching the Pacific; they are watching for signals that can eventually influence East Africa’s atmosphere and rainfall. The immediate concern for Tanzania is the coming autumn season.
Dr Chang’a said the current outlook points to an early start of rainfall in several parts of the country, particularly around the Lake Victoria basin.
“If we refer to the forecast that we have issued for the autumn rains, we clearly stated that we expect the rains to start early in the Lake Victoria zone, meaning Kagera, Geita, Shinyanga, Simiyu, Mwanza and Mara,” he said.
He added that, “In these areas, we expect the rains to start around the fourth week of September towards the first week of October.”
TMA expects rainfall in these areas to be above normal tending towards normal. “But the rains will be above normal tending towards normal,” Dr Chang’a said.
For farmers, early and adequate rainfall can be welcome news, it can improve soil moisture, support crop establishment and provide water for livestock.
But the same rainfall can become destructive if it falls too heavily or over a short period. That is why Dr Chang’a cautions that the rainfall outlook should not be interpreted only as an agricultural opportunity.
“Extreme weather events also cannot be ruled out,” he said, adding that warning carries implications beyond farms.
Heavy rainfall can overwhelm drainage systems, raise river levels, damage roads and bridges, cause flooding and affect communities living in low-lying areas.
From the Lake Victoria basin to the coast
The expected influence of El Niño will not be limited to the Lake Victoria basin. Dr Chang’a said the northeastern highlands are also expected to experience abovenormal to normal rainfall.
“The northeastern highlands, meaning Manyara, Kilimanjaro and Arusha, have also been identified in our statement as areas where we expect rainfall to be above normal tending towards normal,” he explained.
The northern coastal belt is similarly expected to receive significant rainfall “On the northern coast, meaning Tanga, Dar es Salaam and Coast Region, as well as northern Morogoro, and also the islands of Unguja and Pemba, we also expect abovenormal to normal rainfall,” Dr Chang’a said.
In these areas, he expects the rains to begin mainly during the first and second weeks of October.
The differences in onset are important because they demonstrate that El Niño should never be treated as a single national rainfall event.
Tanzania’s geography means that the same climate driver can produce different rainfall patterns from one area to another.
This is why TMA’s regional forecasts are more useful for decision-making than general statements about El Niño circulating online.
The regional climate pictures
Tanzania’s forecast is part of a wider regional pattern. The Intergovernmental Authority on Development’s Climate Prediction and Applications Centre (ICPAC) says El Niño has developed and is expected to strengthen during the remainder of 2026.
Its October-December 2026 outlook indicates a higher likelihood of wetterthan-normal conditions across much of the Greater Horn of Africa.
ICPAC also expects a positive Indian Ocean Dipole (IOD) during the same period, another climate driver that can influence rainfall over East Africa. The interaction between these systems is particularly important.
The Pacific may provide one signal, while the Indian Ocean provides another. When the signals reinforce one another, the probability of wetter conditions over parts of East Africa can increase.
However, scientists caution against assuming that every El Niño produces exactly the same outcome.
ICPAC’s historical analysis shows that local climate drivers can modify the influence of ENSO, meaning that the rainfall outcome of one El Niño event may differ from another.
This is why the forecast for 2026 should be followed through regular updates rather than relying solely on historical comparisons.
How strong is this El Niño?
The strength of the current event is one reason scientists are paying close attention.
World Meteorological Organisation’s (WMO) latest assessment says El Niño is firmly established and is expected to intensify further, with the event forecast to reach very strong intensity before peaking towards the end of 2026.
WMO gives an exceptionally high, nearly 100 per cent probability that El Niño will persist through February 2027.
The organisation’s September-November forecast projects a Niño 3.4 sea-surface temperature anomaly of approximately 3.6°C, with the intensification trajectory expected to peak around November-December.
NOAA’s Climate Prediction Center has similarly reported a rapidly strengthening El Niño, assigning a greater than 90 per cent probability of a very strong event during the Northern Hemisphere autumn and winter of 2026-27.
These forecasts do not mean that Tanzania will experience the strongest possible rainfall everywhere.
The strength of El Niño in the Pacific is only one part of a much larger climate system.
Nevertheless, it provides a strong reason for East African countries to prepare for potentially unusual rainfall conditions.
Tanzania and its neighbours have experienced major El Niño events before. The 1997-98 El Niño remains one of the most significant examples.
Across East Africa, the event was associated with exceptionally heavy rainfall and widespread flooding. The event is still remembered because of the scale of disruption caused across the region.
Another major El Niño occurred in 2015-16, while 2023 also brought unusually wet conditions to large parts of East Africa.
ICPAC identifies 1997 and 2023 as useful analogue years for the current forecast because both were associated with wetter-than-normal October-December conditions across much of the region.
However, the centre emphasises that these historical comparisons are primarily useful for preparedness and that the current forecast should guide present decisions.
The lesson is therefore not that 2026 will repeat 1997 or 2023, the lesson is that extreme rainfall can have consequences that extend far beyond agriculture.
Rain is essential to Tanzania’s economy and livelihoods, but excessive rainfall can create a very different reality.
In rural areas, waterlogged fields can damage crops, in towns and cities, heavy downpours can overwhelm drainage systems.
Rivers can rise rapidly, threatening settlements and infrastructure. Roads and bridges can be damaged, disrupting transportation and trade.
Flooding can also contaminate water sources and increase the risk of water-related diseases. ICPAC’s outlook highlights this double-edged nature of the coming season.
It says wetter conditions can support agricultural production, replenish water resources and improve rangelands, but also warns of increased risks of flooding, flash floods and landslides in vulnerable areas.
This means the question is not simply whether Tanzania needs rain. It is whether the country is prepared for the amount, timing and intensity of the rain that may come.
A warning for cities and infrastructure
The implications are particularly significant for rapidly growing urban areas. When heavy rain falls over a city, the ability of drainage systems to move water safely becomes crucial. Blocked drains, construction over natural waterways and settlements in flood-prone areas can turn intense rainfall into a disaster.
Dar es Salaam and other growing urban centres, therefore, need to treat seasonal forecasts as part of disasterpreparedness planning, the same applies to roads and bridges.
A forecast of increased rainfall provides an opportunity to inspect vulnerable infrastructure before the rains intensify rather than waiting for a bridge to collapse or a road to become impassable.
Water authorities must similarly monitor river and dam levels, while health authorities can prepare for potential increases in waterborne diseases. The value of an early warning system is precisely that it provides time.
What farmers need to understand
For farmers, the message should neither be fear nor complacency. Rainfall brings an opportunity if it arrives at the right time and in manageable amounts.
TMA’s forecast of early rainfall in parts of the Lake Victoria basin may allow farmers to prepare accordingly but farmers also need to follow shorter-term forecasts because a seasonal forecast does not tell them exactly what will happen on a particular day.
Dr Chang’a’s explanation of an earlier strong El Niño provides useful context on how the phenomenon will influence the timing of rainfall.
“Due to the presence of El Niño heading into October, November, December and even early January, periods of heavy rainfall are expected,” he said.
“We may experience early rains from September. However, the autumn rains in general are expected to strengthen more towards October in many areas.”
He also explained that in areas where there is normally one major rainfall season, El Niño can influence the timing of that season.
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“The presence of El Niño towards the end of the year may cause the November rains to start early and continue through April in some areas that receive one rainy season per year, where normally the season begins in November,” he said.
Those remarks help explain the broader mechanism of the phenomenon, while TMA’s current 2026 forecast remains the appropriate guide for the coming season.
El Niño is not climate change
As discussions about the current El Niño increase, another source of confusion has emerged: The relationship between El Niño and climate change. The two should not be treated as the same phenomenon.
El Niño is a naturally occurring fluctuation in the ocean-atmosphere system. Climate change refers to long-term changes in the Earth’s climate, driven predominantly by increasing concentrations of greenhouse gases resulting from human activities
WMO says there is currently no evidence that climate change increases the frequency or intensity of El Niño events.
However, a warmer atmosphere and ocean can influence the intensity of some weather extremes associated with climate variability.
In other words, El Niño is not caused by climate change, but its impacts occur within a climate system that is already warming.
That distinction is important because public understanding of the phenomenon influences how people respond to warnings.
For Tanzania, the arrival of El Niño presents both opportunities and risks. Adequate rainfall will support agriculture, replenish water resources and improve pasture. Excessive rainfall will damage crops, infrastructure and livelihoods.
The difference will partly depend on how well communities and institutions prepare.
TMA’s forecast provides valuable advance information, local authorities must act now to clear drainage systems, farmers need to make informed planting decisions, communities in flood-prone areas must identify safe areas and evacuation routes.
Road and bridge authorities must inspect vulnerable infrastructure, water authorities need to monitor rivers and reservoirs, health authorities must prepare for possible water-related disease outbreaks and citizens need to follow official forecasts as they are updated.
A distant ocean, a local reality
El Niño offers perhaps one of the clearest demonstrations of how interconnected the world’s climate system is.
A change in the temperature of an ocean far from Africa may influence atmospheric circulation.
That circulation affects clouds and rainfall and rainfall can determine whether a farmer gets a good harvest, whether a river remains within its banks, whether a road remains open or whether a community is forced to evacuate.
For Tanzania, the current warning is therefore not simply about rain. It is about timing, intensity, preparedness and resilience.
Dr Chang’a’s message that rainfall is expected to be above normal tending towards normal in several areas, combined with his warning that extreme weather events cannot be ruled out, provides the immediate national context.
The question is whether Tanzania will turn the warning into action before the heavy rains arrive.