Tracking Climate Volatility: An Evaluation of Temperature Trends in Poorly Gauged Coastal Urban Areas

Excessive heat threatens health, productivity, energy systems, infrastructure, and thermal comfort in rapidly urbanizing African coastal settlements, yet quantified information on rising temperature remains limited. This study assessed monthly minimum, mean, and maximum temperatures from 1980 to 2025 at five Tanzanian coastal stations: Tanga Airport, Kibaha Agromet, Port of Dar es Salaam (PoD), Julius Nyerere International Airport (JNIA), and Mtwara Airport. Trends in temperature variables, extreme temperature indices, temperature anomalies, monthly diurnal temperature range, annual temperature range, and month-specific temperatures were evaluated using a pre-whitening Mann Kendall test and Theil–Sen slopes. The findings show that warming occurred at every station, although magnitude and significance varied. Minimum temperatures rose faster than maximum temperatures, particularly at the PoD and JNIA stations, where significant increases reached 0.07 and 0.06 °C per year, respectively. Extreme temperature indices and temperature anomalies also increased significantly at all stations, while monthly diurnal ranges and annual temperature ranges considerably declined at the Tanga Airport, PoD, and JNIA stations. Warming affected both warm and cool seasons, with particularly strong increases in minimum temperatures at the PoD and JNIA stations. Overall, coastal warming is spatially uneven, driven mainly by rising nighttime temperatures, and amplified in dense urban settlements.