Rainy season: May–November 2025. Dry season: December 2025–April 2026. Climate history has separate observation filters; scoring tests use the main assessment period.
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MAIN ASSESSMENT
Heat vulnerability by catchment
Scores combine temperature, humidity and heatwaves with what residents reported in the 2022 survey. Higher scores mean greater heat vulnerability. Use the period menu to compare seasons or selected months.
KEY INFO
- Survey catchments
- 13
- Survey interviews
- 942
- Household survey
- 2022
- Climate history
- 2006–2026
Overall HHVI
Select a catchment on the map or use the selector. Striped shading marks York’s boundary, which needs checking. Areas without shading are outside the mapped catchments.
Monthly HHVIFull-period HHVI · May 2025–April 2026
What goes into the score?
Survey answers and climate readings for this catchment. The contribution of each measure is shown alongside it.
All catchments
SIDE-BY-SIDE
Compare catchment profiles
Compare overall scores and the conditions behind them. Open each section to see the measures, their values and how much they contribute. Higher scores mean greater vulnerability.
CITY CLIMATE
Freetown’s climate history
Daily weather readings cover January 2006–September 2026. They come from station GFLL, returned for Freetown by Wolfram. Eight unusual temperature readings are kept and marked in the data table.
24recorded heatwaves
90heatwave days
23 dayslongest recorded heatwave
~99%of daily readings available
Explore the weather record
Choose a measure, then narrow the period.
Filter daily readings
Daily maximum temperature (°C)
Keep only days within these limits. Monthly and yearly averages will use those days.
Lowest displayed valueHighest displayed valueObserved heatwave day(s)
Averages use only the days you select. Missing readings are left out. Eight unusual temperature readings are kept and marked in the table. A heatwave means the daily high temperature exceeded 33°C for at least two days in a row. Heatwave dates come from the full weather record; they do not show confirmed cases of heat illness.
View selected daily readings
Seasonal temperature profile
Each point is the average for that calendar month across 2006–2025. This chart keeps the full historical pattern when you change the filters above.
Observed heatwave days by year
Heatwaves are at least two days in a row with daily high temperatures above 33°C. Of the 90 recorded heatwave days, 46 occurred in 2007. Missing readings may hide some events. The 2026 record ends in September.
SEPARATE CLIMATE OUTLOOK
Monthly temperature forecasts
October 2026–September 2027. These forecast monthly averages, not daily extremes or heatwave dates. Forecasts never change baseline HHVI scores.
Average daily high
Recommended modelForecast temperatureNarrower range (80%)Wider range (95%)
The shaded bands show a narrower and a wider range around the forecast. They are based on errors in past forecasts. Future temperatures can fall outside these ranges.
Forecast values and ranges
ASSUMPTIONS & UNCERTAINTY
How stable are the priorities?
See how scores, categories and rankings change when measures contribute different amounts, or when temperature, humidity or heatwaves are left out.
Baseline
Main assessment stays unchangedDo catchment rankings change?
All tests use the same dates and category cut-offs. Rank changes show how much the scoring choices matter.
What do the score ranges mean?
We recalculated scores 1,000 times using different draws from the survey responses. The ranges show how the choice of respondents could affect the scores.
The ranges cover differences in survey responses only. They do not cover missing wards, people who did not respond, changes since 2022, map errors or missing health records. Ranges are not shown for tests that change the survey measures’ contribution.
York has only 14 interviews. Their recorded locations are outside the supplied boundary, so its results need extra care.
ABOUT THE ASSESSMENT
How the scores work and their limits
The main assessment covers May 2025–April 2026. The sections below explain the scores, their limits and the separate temperature forecasts.
Who is behind this assessment?
This assessment forms part of the Freetown pilot under C40 Cities’ Accelerating Heat-Health Action in Cities Incubator, working with Freetown City Council to strengthen heat-health resilience. The programme is supported in part by The Rockefeller Foundation.
- Commissioned by
- C40 Cities
- City partner
- Freetown City Council (FCC)
- Project delivery
- Saint Homobonus Limited (HB)
- Climate data analysis and modelling
- Joel Abdulai Kallon · Climate Data Analysis and Modelling Expert, engaged by HB
The scores have not yet been checked against recorded heat-related illness.
How the index is built
HHVI = 40% exposure + 30% sensitivity + 30% Adaptive Capacity Gaps.
Exposure describes heat conditions. Sensitivity covers factors such as age, health and income. Adaptive Capacity Gaps cover cooling, housing, services and heat-protection habits.
Survey percentages use the people who answered each question. Responses are not adjusted to match the population. For service measures, we average answers within each surveyed ward and give those wards equal importance.
Measures use a common scale from 0 to 1. Higher values always mean greater vulnerability. Some measures compare survey percentages directly; others compare values with the lowest and highest across the 13 catchments.
Low, Moderate, High and Very high compare catchments within this assessment. They do not show a clinical risk level or mean that an area is safe from heat.
How weather affects the score
Exposure contributes 40% of HHVI, sensitivity 30%, and Adaptive Capacity Gaps 30%. Within exposure, reported night-time heat contributes 26.67%, reports of rising heat 20%, daily high temperature 13.33%, humidity 13.33%, and heatwave frequency and length 26.67%. Temperature and humidity are scored separately. This is not a calculated heat index.
Temperature and humidity are averaged over the available daily readings in each period. We compare them with a fixed range from the 2006–2024 record, leaving out the lowest and highest 5% of readings. The same range is used for every period so comparisons stay consistent.
A heatwave is at least two days in a row with daily high temperatures above 33°C. Each event belongs to the period in which it started, and its full length is counted. We adjust the event count to the equivalent of 365 days with readings so periods of different lengths can be compared. This is a scoring measure, not a prediction. Historical upper cut-offs come from the 2006–2024 record. Periods with no recorded events score zero for heatwaves.
Weather scores stay between 0 and 1. Category cut-offs are fixed using the main assessment period. Selected months are combined using daily readings before scoring. All catchments share the city weather record, so changing the period changes scores but leaves catchment rankings unchanged.
Assessment periods: the main period is 1 May 2025–30 April 2026. Rainy season covers May–November 2025; dry season covers December 2025–April 2026. Calendar 2025 is a comparison, with an optional multi-month selection. The seasons follow calendar months; the actual start and end of rainfall can vary.
Temperature, humidity and heat index ↗
Monthly score changes come from the weather record. The 2022 survey answers stay fixed. Higher humidity receives a higher exposure score, but the score does not predict illness.
What to keep in mind
2022 survey. Results are not a current household census. Four interviews without consent were excluded.
Uneven samples. Only four catchments have at least 100 interviews; nine listed wards were unsampled.
Map boundaries. 124 interview locations do not match their recorded catchment boundaries, including all 14 York interviews. We keep the catchments recorded in the survey.
Missing health information. Local sensor readings and health-facility records were not available for this analysis. The scores have not been checked against health outcomes.
Housing, work, reported symptoms and coping habits help describe vulnerability, but do not directly measure illness risk. Receiving heat information does not show whether it was understood or used. The share given to each measure is based on analyst judgement.
Stakeholder downloads
Authorised stakeholders can download data and maps from the stakeholder dashboard.