NAIROBI, Kenya — Kenya is already experiencing the influence of El Niño, with the climate phenomenon contributing to prolonged dry spells and unusual temperature patterns in parts of the country, the Kenya Meteorological Service Authority (KMSA) has said.
Climate scientist and Head of Public Weather Services at KMSA Hannah Kimani said El Niño should not be understood simply as a weather event that brings rain or automatically causes flooding.
She said the phenomenon changes global atmospheric circulation and can either enhance or suppress rainfall depending on other climate systems influencing the region.
“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,” Kimani said.
Kimani was speaking during the fifth edition of the Annual Journalists Climate Training (AJCT 5), organised by Power Shift Africa in Kigali, Rwanda.
El Niño already affecting Kenya
El Niño occurs when sea-surface temperatures in parts of the central and eastern equatorial Pacific Ocean become warmer than normal, triggering changes in atmospheric circulation that can influence weather patterns far beyond the Pacific.
According to Kimani, its influence is already evident in Kenya.
Western Kenya and the North Rift would normally receive rainfall between June and September as a continuation of the March-May long-rains season. This year, however, the two regions have experienced depressed rainfall and prolonged dry spells.
The effects have also been seen in temperatures.
Central Kenya and Nairobi typically experience their coldest conditions between June and August, but unusually warm days have been recorded during the current cold season.
“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,” Kimani said.
El Niño does not mean continuous rain
As Kenya approaches the October-November-December (OND) rainfall season, Kimani said El Niño is expected to intensify and is associated with enhanced rainfall during the period.
However, she warned against interpreting an above-normal rainfall forecast as a prediction of continuous rain 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.”
The OND rainfall season occurs in Kenya regardless of whether El Niño is present. The climate phenomenon instead modifies the intensity and distribution of rainfall produced by Kenya’s main rain-bearing systems.
This means an El Niño season can still contain dry days, while individual areas may experience rainfall that differs significantly from the national outlook.
Why El Niño does not automatically cause floods
Kimani said it would be scientifically unsafe to conclude that a strong El Niño will automatically result in disastrous flooding in Kenya.
Other climate systems, including the Indian Ocean Dipole (IOD), Madden-Julian Oscillation (MJO) and tropical cyclones, can significantly influence the amount and distribution of rainfall received in the country.
The Indian Ocean Dipole is particularly important.
During a positive IOD phase, sea-surface temperatures in the western Indian Ocean near the East African coast become warmer than average, while waters closer to Australia are relatively cooler.
The resulting atmospheric conditions can push moisture towards East Africa and encourage cloud formation, potentially increasing rainfall.
Kimani said the interaction between these systems explains why the strength of El Niño alone cannot be used to predict whether Kenya will experience torrential rains.
1997 and 2015 show the difference
Historical rainfall patterns demonstrate the importance of looking beyond El Niño.
In 1997, Kenya experienced a very strong El Niño alongside a very strong positive Indian Ocean Dipole. The combination contributed to the torrential rainfall and flooding that became one of the country’s most memorable weather events.
In 2015, Kenya again experienced a very strong El Niño, but rainfall was not comparable with the 1997 event because the Indian Ocean Dipole was only weakly positive.
Kenya also experienced exceptionally heavy rainfall in 2019 despite there being no El Niño. Instead, the country recorded a very strong positive Indian Ocean Dipole, which contributed significantly to the extreme rainfall.
Kimani therefore cautioned against treating El Niño as a standalone predictor of floods.
“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,” she said.
She cited the March-April-May 2026 rainfall season as another example. Kenya experienced enhanced rainfall across the country despite there being no El Niño at the time.
Kimani attributed the enhanced rainfall to the Madden-Julian Oscillation and a tropical cyclone.
The ITCZ is Kenya’s main rain-bearing system
Kimani said another common misconception is that El Niño itself brings rain to Kenya.
The country’s main rain-bearing system is the Intertropical Convergence Zone (ITCZ), a band of atmospheric convergence that moves north and south with the seasonal position of the sun.
Its movement helps determine Kenya’s two main rainfall seasons: the March-May long rains and the October-December short rains.
The ITCZ shifts southwards towards the Southern Hemisphere before the October-December season before moving northwards again around March.
El Niño, the Indian Ocean Dipole and other atmospheric systems then influence or 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,” Kimani 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’ actually means
Kimani also sought to explain how Kenyans should interpret seasonal rainfall forecasts.
She said “normal rainfall” is not a single amount that applies to the whole country. Meteorologists establish a long-term rainfall average for individual locations using approximately 30 years of historical records.
Rainfall between 75 and 125 per cent of that long-term average is classified as normal.
For example, if an area has a long-term average rainfall of 400 millimetres, rainfall between 300mm and 500mm would fall within the normal range.
Rainfall above 500mm would be considered above normal, while rainfall below 300mm would be below normal.
The thresholds differ from one part of Kenya to another because rainfall patterns vary according to factors including elevation and topography.
Central and western Kenya generally receive more rainfall than arid and semi-arid areas such as Garissa, Mandera, Wajir and Lodwar.
KMSA therefore further downscales national seasonal forecasts to county level to account for these differences.
A 70 per cent forecast is not a guarantee
Kimani said probabilistic forecasts are also frequently misunderstood.
A forecast stating that there is a 70 per cent probability of above-normal rainfall does not mean meteorologists are certain that above-normal rainfall will occur.
Rather, it means there is a 70 per cent likelihood 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 intended to communicate uncertainty, particularly when forecasts cover longer periods.
Seasonal forecasts are updated regularly
KMSA issues seasonal forecasts before the start of major rainfall seasons, but the information is continuously updated through monthly and weekly forecasts.
A seasonal forecast can indicate whether rainfall is likely to be wetter or drier than normal but cannot reliably predict the exact day on which heavy rainfall will occur.
Monthly forecasts provide a shorter outlook, while weekly forecasts offer more detailed information.
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 forecasts consider additional factors such as wind direction, atmospheric moisture, instability and the position of the ITCZ.
Kenya has experienced several El Niño events
Kimani said Kenyans often associate El Niño with the devastating 1997 rains, but the country has experienced several El Niño episodes of varying strength.
Since observations began in 1950, five very strong El Niño events have been recorded in 1965, 1972, 1982, 1997 and 2015.
She said seven El Niño events have occurred since 1997 — in 2002, 2004, 2006, 2009, 2015, 2018 and 2023 — although their intensity and impacts differed.
The history, she said, demonstrates why the 1997 experience should not automatically be used as a template for every El Niño event.
“There is no year that behaves exactly like the other,” Kimani 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.”
The 2023 El Niño was accompanied by a very strong positive Indian Ocean Dipole and contributed to exceptionally heavy rainfall in Kenya.
