Switzerland is enduring its tenth consecutive day of temperatures above 30°C, placing this June among the hottest on record. The month began cool but turned hot. Temperatures rose sharply from the middle of the month, with much of the country surpassing 30°C on June 16th and 17th. The prolonged heat invites comparisons with the exceptional summers of 2003 and 2018, both of which left lasting marks on the country’s environment and agriculture.
The current heat wave already surpasses records in some places. Geneva, Bern, Zurich and Lugano have each recorded ten days above 30°C—already more than during the heat wave in 2018. In Bern, the number of hot days has already exceeded even the 2003 record. Zurich is forecast to record 12 hot days, one more than in 2003. However, the 2003 heat wave will likely remain the record for Geneva (19 days) and Lugano (17 days).
In 2003 high temperatures arrived in June and persisted through much of the summer. June and August were particularly exceptional, producing what became known as the summer of the century. The pattern in 2018 was different. June was relatively moderate before extreme heat arrived in July and August. Unlike 2003, however, unusually warm weather continued into September, making September 2018 warmer on average than September 2003.
The current wave of heat is forecast to endure through the weekend before subsiding, according to Swiss Meteo. Of the 51 forecast scenarios modelled, the overwhelming majority point to a sharp drop in temperatures on Monday, followed by further cooling on Wednesday. The few remaining outlying scenarios also converge on the same outcome by midweek.
Before cooler weather arrives, however, Switzerland is likely to experience one final surge of heat. Ahead of Monday’s cold front, southwesterly winds will draw in warm—but significantly more humid—air. Higher humidity will make conditions feel more oppressive by reducing the body’s ability to cool itself through perspiration, while also keeping overnight temperatures unusually high. As a result, Saturday and Sunday are expected to be the most uncomfortable days of the current heatwave.
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Swiss Meteo blog (in French) – Take a 5 minute French test now
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