Uefa delegates will measure the temperature with a wet bulb globe temperature (WBGT) thermometer at the end of the teams’ warm-ups.
Different from a normal thermometer, the WBGT thermometer accounts for temperature, humidity, wind speed, sun angle and cloud cover to determine the heat.
If the WBGT temperature exceeds 32C, cooling breaks – which can last between 90 seconds and three minutes – will be introduced for players during the match.
If the temperature is below those thresholds, the implementation of drinks breaks is at the discretion of the referee.
A heat warning has been issued by Uefa for all matches on Wednesday, Thursday and Friday, with fans allowed to bring a water bottle up to half a litre in size into the stadium on those days.
Uefa has also encouraged fans to re-fill their bottles and cups in the stadium bathrooms, and to seek shade in the fan zones across the country.
Watch all your favorite Amazon Prime Video Sports broadcasts live and free. Get access to NFL, NBA, NASCAR, WNBA, and more – all included with your Prime membership!