Nairobi — The Kenya Meteorological Department (KMD) has cautioned Kenyans to remain alert for potentially heavy downpours and take necessary precautions as the March-April-May (MAM) Long Rains season sets in.

KMD Director David Gikungu confirmed the onset, noting that rainfall is expected to continue across several parts of the country this week.

"In the forecast for this week, rainfall is expected to continue over several parts of the country," said Gikungu.

He further warned that isolated heavy rainfall events are likely in some areas, particularly over the highlands east and west of the Rift Valley, including Nairobi County, the Lake Victoria Basin, the Rift Valley, the southeastern lowlands, and northeastern Kenya.

Gikungu noted that rains recorded during the week of March 3 to 9, 2025, showed a noticeable increase in rainfall amounts, especially in the southeastern lowlands and parts of the northeastern region.

The subsequent rains recorded during the week of March 10 to 16, 2025, marked the official onset of the MAM 2025 season, particularly for the highlands west of the Rift Valley and the Lake Victoria Basin.

Similar rainfall was also experienced in parts of the Rift Valley, Nairobi, isolated areas over the highlands east of the Rift Valley, the southeastern lowlands, and Isiolo County.

"The onset of the March-April-May (MAM) 'Long Rains' Season is specifically defined as the first day of the wet season when two key conditions are met: a wet spell occurs, characterized by accumulated rainfall of at least 20 mm over three consecutive days," KMD explained.

Required threshold

Additionally, there should be no dry spell--defined as a period with little to no rainfall lasting at least seven days--within the following 21 days to confirm the start of the long rains.

For northern parts of the country, the threshold is slightly lower, with the required accumulated rainfall being at least 10 mm over three consecutive days.

Gikungu said the remaining parts of the highlands east of the Rift Valley and the southeastern lowlands are expected to experience the onset of the season this week.

"The onset for the northeastern region is also expected this week (March 18-24) and next week (March 25-31). However, this is likely to be followed by dry spells," Gikungu added.

He also revealed that the northwestern parts of Kenya and the coastal regions are expected to receive occasional rainfall during the remaining part of March 2025.

According to KMD, the coastal region is expected to experience the peak of the season in May, with the onset likely to occur in April.