Trend and Change-Point Detection of Rainfall and Temperature Extremes in the Northwestern State of Nigeria

Abstract

Insights into temperature and rainfall extremes are essential for managing climate-related risks. This study examines variability and behavior of temperature and rainfall extremes in Kano, a semi-arid city in northwestern Nigeria. Daily observations of maximum temperature and rainfall were analyzed. The focus was on seasonal distribution, event frequency, and possible shifts in extreme conditions. Extreme events were defined using the 95th percentile threshold. This resulted in thresholds of 41.00 °C for maximum temperature and 16.30 mm for rainfall. Trend detection was carried out using the Mann–Kendall test and Sen’s slope estimator. Pettitt’s test was applied to identify change points in event frequency. Seasonal and annual frequencies were also evaluated. Extreme heat events were strongly concentrated in spring, accounting for 98.28% of all heat extremes. Most extreme rainfall events occurred in summer, representing 78.01% of the total. No statistically significant trends were detected for either variable. A slight decline was observed in heat extremes. Change-point analysis indicated a shift in heat extremes after 2016 and in rainfall events around 2020. The findings support the need for localized assessments to guide planning in agriculture and water management in semi-arid regions.