El Niño is already here and has contributed to the prolonged dry spells and unusual temperature patterns experienced in parts of Kenya, the Kenya Meteorological Service Authority (KMSA) has said.
Climate scientist and head of the Public Weather Services Section at KMSA Hannah Kimani said the phenomenon should not be mistaken for rainfall or viewed solely as a precursor to floods.
She said El Niño is a climate phenomenon that occurs when sea surface temperatures in parts of the central and eastern equatorial Pacific Ocean become warmer than usual, altering global circulation patterns and, consequently, rainfall and temperature patterns worldwide.
“El Niño is not coming; El Niño is already here with us. El Niño is not rainfall as most Kenyans believe. It basically changes the patterns in the whole world. In Kenya, it is associated with depressed rainfall or below-average rainfall over the western half of the country and the North Rift,” she said.
Speaking during the 5th edition of the Annual Journalists Climate Training (AJCT 5) by Power Shift Africa in Kigali, Rwanda, Kimani said this influence has already been evident between June and September, when western Kenya and the North Rift normally receive rainfall as a continuation of the March-May season.
This year, however, the two regions have experienced depressed rainfall and prolonged dry spells. The effects have not been limited to rainfall.
Kimani said El Niño has also contributed to changes in temperature patterns, including unusually warm days during what is ordinarily Kenya’s cold season.
Central Kenya and Nairobi typically experience colder conditions between June and August, but this year has also seen extremely warm days.
“El Niño will not stop seasons from happening; it will slightly alter them. We still had cold conditions from June because we are still in the cold season, but because of El Niño we have had extremely warm days,” she added.
As Kenya heads into the October-November-December rainfall season, Kimani said El Nino is expected to intensify and is associated with enhanced rainfall during the period.
However, she cautioned against interpreting an above-normal seasonal forecast to mean the country will experience continuous rainfall or widespread flooding.
“El Niño or above-average rainfall doesn’t mean that it is going to be raining all the time. You can still have some days that are dry even when you’re having El Niño-driven rains.”
She said the October-December rainfall season occurs in Kenya regardless of whether El Niño is present. The phenomenon can instead enhance or suppress rainfall depending on the prevailing conditions and other climate systems.
Why El Nino does not automatically mean floods
Kimani said it would be scientifically unsafe to conclude that a strong El Niño will automatically result in disastrous flooding.
The amount of rainfall Kenya receives is also influenced by other systems, including the Indian Ocean Dipole (IOD), Madden-Julian Oscillation (MJO) and tropical cyclones.
The Indian Ocean Dipole is particularly important, where a positive IOD occurs when sea surface temperatures in the western Indian Ocean, close to the East African coast, are warmer than average while waters near Australia are cooler.
Kimani said this configuration can cause winds carrying moisture to move towards the East African coast. The warm waters then encourage cloud formation, contributing to enhanced rainfall.
Historical events show why the strength of El Niño alone cannot be used to predict the amount of rainfall Kenya will receive.
In 2015, Kenya experienced a very strong El Niño, but did not receive rainfall comparable to that of 1997 because the Indian Ocean Dipole was only weakly positive.
In 1997, a very strong El Niño occurred alongside a very strong positive Indian Ocean Dipole, contributing to the torrential rainfall that Kenyans remember.
In 2019, Kenya experienced very heavy rainfall despite having no El Nino. Instead, the country recorded a very strong positive Indian Ocean Dipole, which contributed to the extreme rainfall.
“I think it would be wrong for someone to say that El Niño is coming or we are having a strong El Niño, therefore we are going to have disastrous floods. This is not scientifically a safe conclusion because we need to look at other factors that actually lead to the torrential rains,” Kimani said.
She cited March-April-May 2026 as another example where Kenya experienced enhanced rainfall across the country during the season despite there being no El Niño .
Kimani attributed the rainfall to the Madden-Julian Oscillation and a tropical cyclone.
She added that another common misconception is that El Niño itself brings rainfall to Kenya.
The country’s main rain-bearing system is the Intertropical Convergence Zone (ITCZ), which contributes to both the March-May long rains and the October-December short rains.
The ITCZ moves with the sun, shifting southwards towards the Southern Hemisphere before the October-December season and returning northwards around March.
Because of its movement, Kenya experiences two main rainfall seasons.
Kimani said El Niño, the Indian Ocean Dipole and other atmospheric systems mainly modify the rainfall generated by the ITCZ.
“The main rain-bearing system in Kenya or in East Africa is what is called the Intertropical Convergence Zone,” she said. “The Indian Ocean Dipole and the El Niño Southern Oscillation just come to modulate or enhance the rainfall that was already brought by the Intertropical Convergence Zone.”
What ‘above-normal rainfall’ means
She also explained what meteorologists mean when they forecast normal, above-normal or below-normal rainfall.
Normal rainfall is not a single figure that applies to the entire country, she said; it is calculated using rainfall records over 30 years to establish the long-term mean for a particular location.
Between 75 and 125 per cent of that long-term mean is classified as normal rainfall.
For example, if an area has a long-term mean rainfall of 400 millimetres, its normal range would be between 300mm and 500mm.
Rainfall above 500mm would be classified as above normal, while rainfall below 300mm would be below normal.
The thresholds vary across the country because different areas have different rainfall patterns, influenced by factors including topography and elevation.
Central and western Kenya, for instance, generally have higher rainfall than arid and semi-arid areas such as Garissa, Mandera, Wajir and Lodwar. This is why KMSA further downscales its national forecast to county level.
A forecast of a 70 per cent probability of above-normal rainfall does not mean the authority is predicting with certainty that above-normal rainfall will occur.
It means there is a 70 per cent probability that rainfall will fall within the above-normal category, while there remains a 30 per cent probability that rainfall could be normal or below normal.
“Unless we are telling you with a hundred per cent probability, which is very rare, that we’re expecting above-normal rainfall, there’s still that small percentage that the forecast could go either way,” Kimani said.
She said probabilistic forecasting is designed to account for uncertainty, particularly when forecasts are issued over longer periods.
KMSA issues seasonal forecasts before a rainfall season begins, but the authority continuously updates them through monthly and weekly forecasts.
A seasonal forecast can indicate that a season is likely to be wetter or drier than normal but cannot reliably identify a specific day on which heavy rainfall will occur.
Monthly forecasts provide a shorter outlook, while weekly forecasts provide greater detail.
As a potentially heavy rainfall event approaches, KMSA can issue weather advisories or alerts, sometimes two to three days before the expected event.
Kimani said short-term weather forecasts also consider factors such as wind direction, moisture or water vapour in the atmosphere, atmospheric instability and the position of the ITCZ.
Kenya has experienced several El Niño events
Kenyans commonly associate El Niño with the 1997 event, but Kimani said the country has experienced several other El Niño episodes.
Since observations began in 1950, five very strong El Niño events have been recorded in 1965, 1972, 1982, 1997 and 2015.
Since 1997, seven El Niño events have occurred in 2002, 2004, 2006, 2009, 2015, 2018 and 2023 with varying intensities.
Some were weak, while others were stronger.
Kimani said this history demonstrates why the 1997 experience should not be used as a template for every subsequent El Niño.
“There is no year that behaves exactly like the other,” she said. “So even if the Indian Ocean Dipole was strong or very strong this year, we would not expect things to be the same as in 1997.”
In the 2023 event, Kenya experienced a strong El Niño alongside a very strong positive Indian Ocean Dipole, contributing to torrential rainfall.