|AU||Perceived Temperature (PT) and Tmin||PT > 35 °C for at least 3 days without night cooling below 20 °C|
Thresholds are subject to modifications depending on weather in preceding days.
|Threshold from epidemiological studies (based on thermophysiological strain) in Germany by DWD adapted to Austria.||Nursing facilities, hospitals and health resorts, childcare facilities (kindergartens, schools, etc.), mobile nursing services, medical chambers and emergency organizations|
|BE||Tmax, Tmin, Tcumul ||Green: No warning, all indices below thresholds.|
Yellow: Tcumul ≥ 17 °C
Orange: 2 day mean with Tmax ≥ 32 °C and Tmin ≥ 20 °C or 3 day mean Tmax ≥ 30 °C and Tmin ≥ 18 °C
Red: 3 day mean Tmax ≥ 32 °C and Tmin ≥ 20 °C
|-||Belgium Interregional Environment Agency (IR-CEL), authorities|
|EN||Tmax and Tmin||Region-specific (for Tmax and Tmin).|
Average thresholds: 30 °C for Tmax and 15 °C for Tmin for at least two consecutive days.
Five alert levels (Levels 0–4).
|Epidemiological (15–20% increased risk of mortality)||National Health Service, local authorities, social care, other public agencies, professionals working with people at risk, individuals, local communities, voluntary groups.|
|FR||Combination of Tmin and Tmax averaged over three days (BMI)||3 days mean of Tmax > regionally dependent thresholds |
3 days mean of Tmin > regionally dependent thresholds
|Biometeorological||Local authorities, Santé Publique France|
|DE||PT and Tmin||Thresholds are region-specific and consider acclimatization (previous 30 days). Benchmark:|
Level 1: 20 °C < PT < 26 °C
Level 2: 26 °C < PT < 32 °C
Level 3—Strong heat stress: 32 °C < PT < 38 °C & Tmin ≥ 17 °C
Level 4—Extreme heat stress: PT ≥ 38 °C & Tmin ≥ 17 °C
Only Levels 3 and 4 are relevant for heat warnings.
|Epidemiological research, based on thermophysiological strain||General public, health system, elderly, people living socially isolated, people needing care, obese persons, chronically ill, working people outdoors, homeless, babies and infants.|
|GR||Tmax and heat index||a. For Tmax over the northern Greek regions:|
35 °C ≤ Tmax < 39 °C (yellow), 39 °C ≤ Tmax < 42 °C (amber), Tmax ≥ 42 °C (red)
b. For Tmax over the Central and Southern parts of Greece:
37 °C ≤ Tmax < 41 °C (yellow), 41 °C ≤ Tmax < 44 °C (amber), Tmax ≥ 44 °C (red)
c. For Tmax over the islands:
33 °C ≤ Tmax < 37 °C (yellow), 37 °C ≤ Tmax ≤ 40 °C (amber), Tmax ≥ 40 °C (red)
Heat index used as a supplementary tool in order to enhance the conclusions from the consideration of each synoptic situation. No thresholds related.
|Climatological percentiles and the respective literature||General Public. Other target groups are managed by the Ministry of Health|
|HU||Tmean||Yellow: 25 °C > Tmean > 27 °C |
Orange: 27 °C > Tmean > 29 °C
Red: Tmean ≥ 29 °C
|Epidemiological, link to mortality||National Public Health and Medical Officer Service|
|IT||Tappmax and “air mass-based approach” in larger cities||City-specific||Epidemiological, related to excess of mortality||Ministry of Health, local health authorities, local civil protection, stakeholders (hospitals, retirement homes etc.) GPs, health resorts, media, registered individuals|
|NE||Tmax||more than 10% probability of 4 or more days with |
Tmax > 27 °C
|Practical: not too many warnings in a year||Elderly, people in care institutions, and chronically ill and overweight people. Public health services, trade associations and the Dutch Red Cross|
|NM||Tmax||Monthly thresholds for each of the 4 phases for 13 cities in 6 regions from May to September||-||Retirement homes, GPs, workers.|
|PT||For heat wave definition: TemperatureFor alert levels: ÍCARO index||Heat wave: Temperature > 32 °C for at least 2 days|
Level 1 & 2: ÍCARO index < 0.31
Level 3: ÍCARO index 0.31–0.93
Level 4 (Heat-wave alert): ÍCARO index > 0.93
|Epidemiological||Portuguese National Institute of Health, the Portuguese Meteorological Institute, Portuguese General Health Directorate and the Portuguese Civil Protection Service|
|RO||Tmax||Alert: Tmax 35–38 °C, Maximum response: Tmax 35–40 °C||-||-|
|SL||Tmean and Tmax||Yellow: Tmax > 31 °C|
Orange: Tmax > 34 °C and/or Tmean > 26 °C
Red: Tmax > 37 °C and/or Tmean > 28 °C
Tresholds are regionally-based
|Climatology-based percentiles||Public (general population), civil defense in case of orange or red warning|
|SP||Heat wave: TmaxHHAP: Tmax and Tmin||Heat wave: At least 3 days with at least 10% of stations in the region with Tmax > 95th percentile. Warnings for single-day events (yellow | orange | red corresponding to different Tmax for each region: North 34 | 37 | 40; Center and Med. 36 | 39 | 42; South 38 | 40 | 44).|
Level 1: 1–2 days Tmax and Tmin above threshold simultaneously
Level 2: 3–4 days above threshold
Level 3: 5 days above threshold
|Heat wave: Climatological percentiles for each region.|
HHAP: temperature triggering mortality.
|General population, Civil Protection, Maritime Rescue Centers, Department of Traffic, Military Unit for Emergencies, Red Cross, other Met Services, government and ministries, media.|
|SW||Tmax||Heat warning class 1: Tmax ≥ 30 °C for 3 or 4 days |
Heat warning class 2: Tmax ≥ 30 °C for at least 5 days or Tmax > 33 °C for at least 3 days.
Notification: Tmax ≥ 26 °C for at least 3 days.
Risk: same thresholds as for the class 2 warning,
but the risk concept is used when the forecast is more uncertain.
“notification” and “risk” are not considered warnings
|Epidemiological, based on the relation between temperature and rate of mortality.||General public and health providers as hospitals, elderly care etc.|
|CH||Heat index ||Level 3 (orange): at least 3 days with HI > 90|
Level 4 (red): at least 5 days with HI > 93
|-||Construction industry, the trade unions (e.g., UNIA) and cantonal authorities|