The study deals with the analysis of monthly rainfall trends and variability over Tanzania. The
monthly rainfall data from 1982 to 2012 was obtained from the Tanzania Meteorological
Agency, Dar es Salaam, Tanzania. The monthly rainfall data from representative stations in the
homogeneous rainfall zones over Tanzania were analyzed for trends by graphical and statistical
Methods. In order to achieve the main and specific objectives, the data were subjected to various
analyses including quality control. The core methodology used in analysis of rainfall trends and
variability over Tanzania were the time series analysis, single mass curve analysis, coefficient of
variation and spatial analysis using surfer program. The results from the study showed that there
were trends in the rainfall data for all stations used. However the trends are not significant except
in Tanga and Pemba. Also results from seasonal and annual coefficient of variation found that
the largest value of variability was observed during OND at Kilimanjaro while the lowest
variability was found in Kigoma, Sumbawanga and Mbeya during November-April (NA) season
which implies that rainfall in these regions is very reliable and Kilimanjaro rainfall is less
reliable. Moreover result from spatial analysis revealed that Bukoba region has the highest mean
annual rainfall followed by Zanzibar and Pemba. The lowest mean annual rainfall was at
Kilimanjaro, which confirms that Kilimanjaro received lowest amount of rainfall. Furthermore
the study has demonstrated that there are both spatial and temporal variability of rainfall over
Tanzania. These findings may be used for monitoring and forecasting extreme weather events
like droughts and floods. This would therefore contribute significantly to the effective
management and sustainable development of the national social economic activities which are
heavily rain- dependent.