Heat Threshold Reports: Honduras and Tanzania
Effective heat early warning systems depend on knowing what “extreme” actually means in a given place, and that definition varies significantly by local climate, population acclimatization, and urban context. This page brings together two technical reports produced by the IFRC Climate Centre that develop locally calibrated heat thresholds for cities in Honduras and Tanzania, providing an operational foundation for heat early warning systems in contexts where such systems are absent, incomplete, or not yet tailored to heat risk.
Honduras: Calibrating the Trigger in Choluteca
The Honduras report focuses on Choluteca — one of the hottest cities in Central America — where even a “normal” day can exceed temperatures that would be considered extreme elsewhere. Using over 60 years of daily maximum temperature data from the Choluteca meteorological station and developed in close collaboration with Honduras’s national meteorological authority (CENAOS), the analysis derives monthly percentile-based thresholds across three alert levels: Watch Monitoring (P90), Alert (P95), and Dangerous (P99). Peak risk months — March through May and July to August — carry thresholds reaching up to 40.6°C at the P99 level. The report proposes a graduated alert framework directly linked to anticipatory action protocols, with CENAOS committed to integrating the thresholds into its operational forecasting products.
Tanzania: City-Specific Thresholds for Dar es Salaam and Zanzibar
The Tanzania report addresses the need for heat thresholds in two of the country’s key urban centers, using station-based temperature data covering 2000–2024 alongside the CHIRTS gridded dataset for broader national coverage. The analysis reveals meaningful differences between cities — both in threshold values and in heatwave patterns — underscoring why a single national standard would be inadequate. In Dar es Salaam, the 90th percentile threshold sits at 33.6°C overall, rising to 34.5°C in the hottest months; Zanzibar’s monthly thresholds reach approximately 35°C in February–March. The report concludes with a practical early warning activation framework and recommendations for integrating thresholds into routine meteorological and public health advisories, with findings shared with the Tanzania Meteorological Authority for review.