In this research project we investigate the extent of possible trends in rainfall patterns and fit Markov
chain models to assess and measure the El Nin˜o/Southern Oscillation (ENSO) effect, i.e. the extent
to which the pattern of rainfall is the same in El Nin˜o, La Nin˜a and normal years. We analysed forty
four years of daily rainfall data and forty years of temperature data from Kigali station in Rwanda. In
order to assess the evidence for change in rainfall, we applied a trend analysis on annual rainfall totals,
number of rain days, mean rain per rain days, seasonal rainfall totals for the short and on long rainy
seasons. Finally, we fit a second order Markov chain model on the data to see whether the pattern
of rainfall in Rwanda is the same in the three categories of years. The results shows that we did not
find a conclusive evidence of climate change in the rainfall trends. Also, the study shows that there are
indications supporting that there may be an effect and this should be investigated further by making a
statistically significant difference between the different types of years.