Speaking to 20 Minuten, Roger Perret from MeteoNews said Wednesday could be the hottest day of the year so far.
And with high temperatures comes an increase in ozone at ground level, which can be harmful.
Situated at an altitude of between 10 and 30 kilometres above the earth, the ozone layer absorbs the dangerous UV radiation of the sun.
However at ground level ozone can cause respiratory troubles in humans and restricted growth in plants.
“The limit was reached on Monday,” said Perret, adding that on Tuesday and Wednesday ozone limits will be “significantly exceeded” in cities and urban areas.
Experts advise people exercise caution in the heat, particularly asthma sufferers, children and those with cardiovascular problems.
Speaking to the paper, Myriam Flühmann of Lung Zurich advised avoiding exercising outside between 11am and 7pm, or if you must, to head to forested areas where the air is cooler.
“Ozone can cause an inflammatory reaction in the airways and restricted lung function,” she said.
Within asthmatics high ozone levels can “worsen existing symptoms,” she added.
Wednesday's temperatures could reach 36C. Source: Meteo Suisse
Last summer’s record-breaking temperatures led ozone limits to be exceeded on 42 days in Zurich to the end of August, said Lung Zurich.
Last July authorities in Geneva temporarily reduced the price of public transport to encourage people to leave their cars at home when ozone levels spiked during the heatwave.
The move came as Switzerland bathed in temperatures up to 38C, driving an increase in air pollution.
According to Meteo Suisse the country won’t quite beat that in the next two days, but temperatures should hit a sweltering 36C in some areas before storms bring cooler air from Thursday onwards.
Switzerland's weather has been erratic of late, with periods of hot weather interspersed with sudden temperature drops.
Last week snow fell in alpine areas down to 1,600m altitude.