Kota Kinabalu is located near the equator with a typically tropical climate, abundant rainfall, high and uniform temperatures, plentiful sunlight and high humidity that comes almost all year. The main economic activities in Kota Kinabalu such as agriculture, fishery, and tourism are highly impacted by the monsoon climate. This study analyzed the monthly time-variability of rainfall and solar radiation in Kota Kinabalu and monsoon temporal from October 2013 to September 2014. The daily average rainfall data were collected from Kota Kinabalu Meteorological Department, while, the solar radiation data with a ten minutes interval were obtained using LI-200 pyronometer. Subsequently, the maximum and minimum monthly average of solar radiation and cumulative rainfall were obtained. The paper examines the observed fluctuation of these variables and attempts to explain their possible relationship. The findings indicate that the period when the southwest monsoon season brings greater rainfall has lesser solar radiation. However, the level of solar radiation does not have an inverse relationship with rainfall amount. This could be due to the variation in air mass, short-term high-intensity rainfall or diurnal variation of rainfall. The city also received higher amount of rainfall in inter-monsoon period in October 2013 than that in the inter-monsoon in April 2014. This phenomenon happened due to the tail effect of typhoons that happen in Philippines. Sudden increases in wind speed up to average 33 km/h also happened during this inter-monsoon period.