Seasonal Variability of Rainfall and Thunderstorm Patterns in Kenya


  • Mary Kurgat

    Department of Earth and Climate Sciences, University of Nairobi, Nairobi, 00100-30197, Kenya

  • Wilson Gitau

    Department of Earth and Climate Sciences, University of Nairobi, Nairobi, 00100-30197, Kenya

Received: 11 December 2023 | Revised: 15 January 2024 | Accepted: 28 January 2024 | Published Online: 29 January 2024


This paper presents an analysis of spatial and temporal variation of rainfall and thunderstorm occurrence over Kenya from January 1987 to December 2017. The meteorological data used were obtained from the Kenya Meteorological Department (KMD) for the same period. This included the monthly thunderstorm occurrences and rainfall amounts of 26 synoptic stations across the country. The characteristics of monthly, seasonal and annual frequency results were presented on spatial maps while Time series graphs were used to display the pattern for annual cycle, seasonal variations and the inter-annual variability of rainfall amounts and thunderstorm occurrences. A well-known non-parametric statistical method Mann Kendall (MK) trend test was used to determine and compare the statistical significance of the trends. Thunderstorm frequencies over the Eastern, Central and Coast regions of the country showed a bimodal pattern with high frequencies coinciding with March-April-May (MAM) and October-November-December (OND) rainy seasons. Very few thunderstorm days were detected over June-July-August (JJA) season. The areas to the western part of the country, near Lake Victoria, had the highest thunderstorm frequencies in the country over the three seasons: MAM, JJAS and OND. The annual frequency showed a quasi-unimodal pattern. These places near Lake Victoria showed significantly increasing thunderstorm trends during the MAM and OND seasons irrespective of the rainfall trends. This shows the effects of Lake Victoria over these areas, and it acts as a continuous source of moisture for thunderstorm formation. However, most stations across the country showed a reducing trend of thunderstorm frequency during MAM and JJA seasons. The importance of these findings is that they could support various policy makers, and users of climate information, especially in the agriculture and aviation industries.


Rainfall, Thunderstorm, Lake Victoria, Kenya, Mann Kendall


[1] Okoola, R.E., 2005. Transition from the Southern to the Northern Hemisphere summer of zones of active convection over the Congo Basin. Meteorology and Atmospheric Physics. 84, 255–265. DOI:

[2] Yuhua, O., Ping, Y., 2012. Audible thunder characteristic and the relation between peak frequency and lightning parameters. Journal of Earth System Science. 121, 211–220. DOI:

[3] World Meteorological Organization (WMO), 1992. International meteorological vocabulary. World Meteorological Organization: Geneva.

[4] Lavigne, T., Liu, C., Liu, N., 2019. How does the trend in thunder days relate to the variation of lightning flash density?. Journal of Geophysical Research: Atmospheres. 124(9), 4955–4974. DOI:

[5] Chaggar, T.S., 1977. Geographical distribution of monthly and annual mean frequency of thunderstorm days over Eastern Africa. EAMD Technical Memorandum No.26.

[6] Temporal Distributions of Global Thunder Days [Internet]. Illinois Department of Energy and Natural Resources. Available from:

[7] Enno, S.E., Piia, P., Agrita, B., et al., 2014. Long-term changes in the frequency of thunder days in the Baltic countries. Boreal Environmental Research. 19, 452–466.

[8] Changnon, S.A., 1981. Possible effects of contrail generated cirrus on mid-western cloud and sunshine. Journal of Applied Meteorology. 20(8).

[9] Wu, C., 2005. Inherent delays and operational reliability of airline schedule. Journal of Air Transport Management. 11(4), 273–282. DOI:

[10] Bhattacharya, S., Bhattacharyya, H.C., 2023. A comparative study of severe thunderstorm among statistical and ANN methodologies. Scientific Reports. 13, 12038. DOI:

[11] Maloba, S., 2015. Spatial and temporal characteristics of thunderstorms over the eastern region of Lake Victoria Basin in Kenya [Master’s thesis]. Nairobi: University of Nairobi.

[12] Ayugi, B.O., Wang, W., Chepkemoi, D., 2016. Analysis for spatial and temporal patterns of rainfall variations over Kenya. Journal of Environmental and Earth Science. 6(11), 69–83.

[13] Ongoma, V., Chen, H., 2017. Temporal and spatial variability of temperature and precipitation over East Africa from 1951 to 2010. Meteorology and Atmospheric Physics. 129, 131–144. DOI:

[14] Gitau, W., Camberlin, P., Ogallo, L., et al., 2018. Trends of intraseasonal descriptors of wet and dry spells over Equatorial eastern Africa. International Journal of Climatology. 38(3), 1189–1200. DOI:

[15] The Thunderstorm. Report of the Thunderstorm Project [Internet]. U.S. Government Printing Office. Available from:

[16] Koros, D., 2014. Determining convective precipitation using cold cloud top temperatures and its impact on aviation industry over western Kenya [Master’s thesis]. Nairobi: University of Nairobi.

[17] Gamoyo, M., Reason, C., Obura, D., 2015. Rainfall variability over the East African coast. Theoretical and Applied Climatology. 120, 311–322. DOI:

[18] Palmer, P.I., Wainwright, C.M., Dong, B., et al., 2023. Drivers and impacts of Eastern African rainfall variability. Nature Reviews Earth & Environment. 4, 254–270. DOI:

[19] Pinzari, L., Mazumdar, S., Girosi, F., 2018. A framework for the identification and classification of homogeneous socioeconomic areas in the analysis of health care variation. International Journal of Health Geographics. 17, 42. DOI:

[20] Mann, H.B., 1945. Nonparametric tests against trend. Econometrica. 13(3), 245–259. DOI:

[21] Kendall, M.G., 1975. Rank correlation methods. Charles Griffin: London..

[22] Mallick, J., Talukdar, S., Alsubih, M., 2021. Analysing the trend of rainfall in Asir region of Saudi Arabia using the family of Mann-Kendall tests, innovative trend analysis, and detrended fluctuation analysis. Theoretical and Applied Climatology. 143, 823–841. DOI:

[23] Gadedjisso-Tossou, A., Adjegan, K.I., Kablan, A.K.M., 2021. Rainfall and temperature trend analysis by Mann-Kendall test and significance for Rainfed Cereal Yields in Northern Togo. Sci. 3(1), 17. DOI:

[24] Aditya, F., Gusmayanti, E., Sudrajat, J., 2021. Rainfall trend analysis using Mann-Kendall and Sen’s slope estimator test in West Kalimantan. IOP Conference Series: Earth and Environmental Science. 893. 012006. DOI:

[25] Asnani, G.C., 2005. Tropical meteorology: Special features of tropical meteorology; Climatology of the tropics; Climatic change; Physics and dynamics of monsoon.

[26] Obiero, K., 2013. Thunderstorm hazards and their impact in the Lake Victoria basin of Kenya [Master’s thesis]. Nairobi: Kenyatta University.

[27] Nakamara, K., 1968. Equatorial Westerlies over East Africa and their climatological significance. Geographical Review of Japan. 41(6), 359–373.

[28] Okoola, R.E., 1999. Mid-tropospheric circulation patterns associated with extreme dry and wet episodes over equatorial Eastern Africa during the northern hemisphere spring. Journal of Applied Meteorology and Climatology. 38(8), 1161–1169. DOI:<1161:MCPAWE>2.0.CO;2

[29] Liebmann, B., Hoerling, M.P., Funk, C., et al., 2014. Understanding recent eastern horn of Africa rainfall variability and change. Journal of Climate. 27(23), 8630–8645. DOI:


How to Cite

Kurgat, M., & Gitau, W. (2024). Seasonal Variability of Rainfall and Thunderstorm Patterns in Kenya. Journal of Atmospheric Science Research, 7(1), 106–117.


Article Type