Kenya is set to experience above average rainfall during the October to December 2026 short rains season, with the Kenya Meteorological Service Authority (KMSA) warning of prolonged wet spells and occasional isolated storms in several parts of the country.
The forecast, issued on Wednesday, August 26, shows that above average rainfall is expected across much of the country.
The areas include Nairobi, Mombasa, Kisumu, Nakuru, Machakos, Makueni, Kitui, Garissa, Wajir, Mandera, Meru, Embu, Kiambu, Kakamega, Bungoma, Kisii, Homa Bay, Migori and Narok.
Near average to above average rainfall is expected in Turkana and parts of West Pokot, Samburu and Marsabit.
KMSA said the October to December season is particularly important in several counties, where it contributes more than 40 per cent of the annual rainfall.
The authority said the season is influenced by several climate systems, including the Intertropical Convergence Zone, the Indian Ocean Dipole (IOD), El Niño, the Madden Julian Oscillation and tropical cyclones developing over the Southwest Indian Ocean.
According to the latest assessment, the 2026 El Niño event is continuing to intensify across the central eastern equatorial Pacific.
“The latest weekly Niño 3.4 index, centred on 12 August 2026, reached +2.7°C,” KMSA said. The authority said the development indicates that El Niño is strengthening further and evolving towards a very strong event.
The Indian Ocean Dipole is currently neutral, although KMSA expects it to increase and potentially cross the positive threshold from September.
“As of 23 August 2026, the weekly IOD index stood at +0.17°C which is below the positive IOD threshold (+0.4°C),” the authority said.
KMSA said sustained IOD values above the threshold for eight consecutive weeks are required before a positive IOD event is considered established.
The authority expects rainfall to be fairly to well distributed in time and space across several parts of the country.
However, distribution is likely to be poor to fair in Turkana and Samburu.
“This season will be marked by prolonged wet spells and occasional isolated storms over several parts of the country,” KMSA said.
The onset of the rains will vary across the country. In 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, rainfall is expected to continue from September into January.
In Nairobi, Kiambu, Meru, Embu, Tharaka Nithi, Nyeri, Kirinyaga, Murang’a, Nyandarua and Laikipia, the rains are expected to begin during the second to third week of October and continue into January.
Machakos, Kitui, Makueni, Kajiado, Taita Taveta and inland parts of Tana River are expected to receive the rains from the third to fourth week of October.
The coastal counties of Mombasa, Kwale, Lamu, Kilifi and the Tana Delta are expected to experience onset between the second and third week of October, with the rains likely to end during the first or second week of December.
Turkana and Samburu are expected to have the latest onset, between the third and fourth week of October, with cessation projected for the first week of December.
KMSA said the probability of mild, moderate or severe drought is low across most parts of Kenya.
However, Turkana has a 15 to 20 per cent chance of experiencing a mild drought event.
The authority also forecasts warmer than average temperatures during the season, particularly in Kwale, Mombasa, Kilifi, Lamu and parts of Tana River, Taita Taveta and Garissa.
KMSA urged the public and stakeholders to follow subsequent forecasts and advisories because some rainfall variations can only be predicted at shorter lead times.
“It is therefore imperative to stay up to date with subsequent forecasts and updates,” the authority said.