Rio's Heat Levels: a five-tier extreme-heat protocol
Decree 54.740 of 28 June 2024 gave Rio five heat levels, set from a forecast heat index recalculated every four hours: communication only at Calor 2 and 3, cooling centres and possible cancellation of outdoor events at Calor 4, and suspension of outdoor school activities and high-risk outdoor work at Calor 5. The forecast sets the level, but the responses are steered by a three-agency committee and approved by the mayor, and the decree's verbs are permissive — even at the top tier, interruption "poderá ser indicada". The only enforcement the decree names covers events with crowds. Calor 4 was declared for the first time in February 2025.
Calor 4 — the lowest tier that opens cooling centres and allows outdoor events to be called off — was declared for the first time in February 2025. No evaluation of the protocol's effect on heat illness or mortality has been published.
🎓 Lesson
A threshold can be precise and still bind nobody. Rio computes its level from a number, then routes every consequence through the mayor's approval, and the city's own favela sensors have read almost 10°C hotter than the official station the level is built on.
Evidence📰 Media
Scale🏙️ City-wide
Sources
↗ Decreto Rio nº 54.740 de 28 de junho de 2024 (Diário Oficial)Primary instrument, read in full. Art. 4º creates five levels; Art. 2º III specifies numerical forecast models for temperature, humidity and heat index over three days "atualizados a cada 4 (quatro) horas"; Art. 4º IV and V use the permissive "poderá ser indicada" for adaptation at Calor 4 and interruption at Calor 5; Art. 5º makes COR responsible for monitoring and publishing levels; Art. 6º limits enforcement to public-concentration activities via GP/AEGE and SEOP; Art. 7º–8º create the CDPECE committee (COR, SMS, SMAC). Signed Eduardo Paes, published 1 July 2024.
↗ Centro de Operações e Resiliência — Níveis de CalorOperator page giving the threshold bands: NC2 36–40°C for 1–2 consecutive days; NC3 36–40°C for 3+ days; NC4 40–44°C for 3+ days; NC5 above 44°C for 3+ days. Lists actions per tier (communication at 2–3; cooling centres, hydration points and possible event cancellation at 4; suspension of high-risk outdoor activity, six-hourly bulletins and suspension of outdoor school activities at 5). Carries the decisive sentence on discretion: "Todas as ações serão orientadas pelo Comitê de Desenvolvimento de Protocolos para Enfrentamento de Calor Extremo e aprovadas pelo prefeito."
↗ Agência Brasil — Cidade do Rio de Janeiro atinge nível 4 de calor (17 Feb 2025)Supports the first Calor 4 declaration, February 2025. Headline level only — the article body returned an electoral-legislation unavailability notice to automated fetch on 26 July 2026. The date and level are corroborated by ClimaInfo and MixVale of the same day. Cooling-point counts reported alongside it could not be confirmed sentence-level and are deliberately not carried in this entry.
↗ Agência Brasil — Calor desigual impulsiona monitoramento do clima em favelas do Rio (29 Mar 2026)Counterweight, verified sentence-level. Rio's Observatório do Calor, a city-hall project measuring heat islands in favelas, recorded a peak of 43.92°C at Morro do Adeus in Complexo do Alemão on 26 December, while "a temperatura máxima oficial na cidade, medida pelo Sistema Alerta Rio, foi de 34ºC" the same day. Expansion to Manguinhos and Salgueiro with UFRJ and UERJ support. Cited as an independent finding about the accuracy of the network the heat levels are computed from; the Observatório is a separate project and is not folded into this entry.
↗ COR — Prefeitura do Rio apresenta ações para possível intensificação do El Niño (20 July 2026)Currency: strongest recent source. Confirms the protocol is live and being prepared for the 2026–27 season against a forecast strong El Niño over October–December, and that "O monitoramento meteorológico é feito de forma integrada pelo COR e pela SMS". The cooling-point count circulating in coverage of this announcement is not present in the text and is therefore not used.
1001 Smart Cities (2026). “Rio's Heat Levels: a five-tier extreme-heat protocol” — Rio de Janeiro, Brazil. The Smart City Atlas. https://1001smartcities.org/projects/rio-heat-protocol/ (last verified 2026-07-26). Data: CC BY 4.0.
The underlying data is free to reuse with attribution — see the open data page.
