NAIROBI, Kenya, Aug 26 — Kenya is set for an enhanced October-December short rains season, with above-average rainfall expected across much of the country and prolonged wet spells likely to be accompanied by isolated storms, the Kenya Meteorological Service Authority (KMSA) has forecast.
The outlook, presented during the 13th National Climate Outlook Forum on Wednesday, projects above-average rainfall across 80 per cent of the country, with rainfall expected to be fairly to well distributed over several areas.
KMSA said the October–December 2026 “Short Rains” season “will be marked by prolonged wet spells and occasional isolated storms over several parts of the country.”
The forecast comes as a strengthening El Niño event develops over the central-eastern equatorial Pacific, while the Indian Ocean Dipole (IOD) — a climate driver defined by the temperature difference between the western and eastern tropical Indian Ocean — remains neutral but is expected to move into its positive phase from September.
KMSA said the latest weekly Niño 3.4 index, centred on August 12, had reached +2.7°C, indicating that El Niño is strengthening towards a very strong event.
The IOD stood at +0.17°C as of August 23, below the +0.4°C threshold required for a positive event.
KMSA expects the index to surpass the threshold from September, although uncertainty remains over the timing and strength of the shift.
“The current IOD value is expected to increase in magnitude and surpass the threshold from September 2026 although some uncertainty remains regarding its timing and strength,” the authority said.
When the rains will begin
The onset of the rains will vary across the country, with some western counties expected to continue receiving rainfall from September while most other areas will see the short rains begin between October and November.
Counties including Nandi, Kakamega, Vihiga, Bungoma, Siaya, Busia, Baringo, Nakuru, Trans Nzoia, Uasin Gishu, Elgeyo Marakwet, West Pokot, Kisii, Nyamira, Kericho, Bomet, Kisumu, Homa Bay, Migori and Narok are expected to continue receiving rainfall from September, with the season extending into January.
In Nyandarua, Laikipia, Nyeri, Kirinyaga, Murang’a, Kiambu, Meru, Embu, Tharaka-Nithi and Nairobi, onset is expected between the second and third weeks of October, with rains continuing into January.
The third to fourth week of October is expected to mark the onset in Machakos, Kitui, Makueni, Kajiado, Taita-Taveta and inland parts of Tana River, with rainfall continuing into January.
In Mombasa, Kwale, Lamu and Kilifi, as well as the Tana Delta, rains are expected between the second and third weeks of October before easing between the first and second weeks of December.
For Marsabit, Mandera, Wajir, Garissa and Isiolo, onset is also expected between the second and third weeks of October, with the season expected to end between the first and second weeks of December.
Turkana and Samburu are expected to experience onset between the third and fourth weeks of October, with rains ending in the first week of December.
Prolonged wet spells, isolated storms
“The OND 2026 rainfall is expected to be fairly to well distributed, both in time and space, over several parts of the country,” the authority said.
Turkana and Samburu are the exceptions, with rainfall distribution expected to range from poor to fair.
The authority said the short rains are particularly important in the country’s eastern and northeastern regions, including Garissa, Wajir, Mandera, Marsabit, Isiolo, Meru, Tharaka-Nithi, Makueni, Kitui, Taita-Taveta and Machakos, where the season contributes more than 40 per cent of annual rainfall.
Some parts of the country receive more than 700mm during the season.
Warmer coastal temperatures, low drought risk
While enhanced rainfall is forecast across much of Kenya, temperatures are also expected to be warmer than average, particularly along the coast.
“Mean temperatures are predicted to be warmer than average during the season with higher probabilities over Kwale, Mombasa, Kilifi, Lamu and parts of Tana River, Taita/Taveta and Garissa Counties,” KMSA said.
The authority said the OND season is generally warm, with mean temperatures ranging from about 17°C in parts of Kericho and Uasin Gishu to more than 30°C in parts of Turkana.
The enhanced rainfall outlook also points to a generally low risk of drought during the season.
KMSA’s Standardized Precipitation Index forecast indicates a low probability of mild, moderate or severe drought across most of the country.
Turkana, however, faces a 15 to 20 per cent chance of a mild drought event.
KMSA said shorter-term climate drivers, including tropical cyclones over the Southwest Indian Ocean and the Madden-Julian Oscillation, could influence rainfall intensity during the season.
“It is therefore imperative to stay up to date with subsequent forecasts and updates,” the authority said.
KMSA urged farmers, communities and other stakeholders to use the outlook alongside its 24-hour, five-day, seven-day and monthly forecasts, as well as regular county-level advisories, to guide planning and decision-making.
