If the government-sponsored "Worklimate" site indicates a "high" risk for Italy's capital, 54-year-old Varricchio and fellow workers at the ancient Rome ruins can stop work at 12:30pm.

With a torrid heatwave punishing much of Europe, 15 out of Italy's 20 regions -- including Lazio, which takes in Rome -- have passed ordinances halting outdoor work in the sun between 12:30pm and 4:00pm if temperatures exceed certain thresholds.

The regulations are particularly geared to construction site and agricultural workers and could potentially affect some three million people, according to one newspaper.

On Wednesday, with noon temperatures hovering at 35 degrees Celsius (95 Fahrenheit), "Worklimate" placed Rome on the list of cities where building sites must close when the sun reaches its zenith.

"The big problem is the humidity, you can't breathe," said Varricchio.

"Working in archaeological excavations, below ground level, it's even more difficult."

Since the ordinance came into force, workers at the Forum -- who are uncovering parts of Emperor Vespasian's Temple of Peace -- have started at 5:30am, instead of 7:00am, in order to end just after midday.

That might offer some respite, but not a lot, as early morning temperatures have exceeded 30 degrees in recent days.

- Suffering -

Health authorities placed 18 Italian cities under red alert Wednesday, warning that the heat can be dangerous even for healthy individuals.

Elena Civitelli, an archeologist with two decades of experience, also suffered at the Forum site this week.

She told AFP she could not remember "suffering so much in the early hours of the morning".

"From 6:00am there's no fresh air," she said.

"Here the workers do a lot of manual labour: with pickaxes, wheelbarrows and shovels, so it's a good thing we finish at 12:30, because working in the afternoon wouldn't be possible."

Above the ruins, tourists seek shade under trees and along walls to escape the sun, lured by restaurant waiters who, despite the heat, remain in the middle of the sidewalks to attract customers.

"It kills you... This morning at 8 o'clock I was already sweating a lot," said Emanuele, 38, who wakes up between 2:00am and 3:00am to deliver fruit and vegetables to Rome restaurants.

"You feel your whole body in pain."

Despite the restrictions, heat-related accidents in the workplace continue, most recently Monday, when the head of a construction company died from heat exposure near Bologna, in central Italy.

Workplace accidents -- and deaths -- are not uncommon in Italy, with 797 work-related deaths last year, according to government statistics.

Many say that security measures are often flouted.

One Rome worker, who preferred to remain anonymous, told AFP that the heat ordinance was not always respected on construction sites in the capital.

"Just walk around the city, and you'll always see them working," he said.