The lack of rainfall since spring has affected even plants that thrive in hot and dry conditions.
In San Casciano, near Florence, the soil, parched by the scorching sun, is not producing enough olives.
Without water, many flowers fall to the ground before becoming oily fruit.
Grower Filippo Legnaioli fears oil production this year could drop by as much as 50-60%.
"We expect a poor season in terms of quantity of olive production. Unfortunately, climactic issues had a decisive influence. We had a very dry spring with practically no rainfall from March to today and this happened at a crucial time during the transition from flower to fruit. We had excellent flowering, but unfortunately, the lack of water hindered the process."
In Castellina in Chianti, September is normally the month of the grape harvest, as it is throughout the country.
But with extreme and prolonged temperatures, the bunches of grapes have ripened earlier than expected.
Sergio Zingarelli is vice-president of the 'Chianti Classico' forum.
"We have smaller grapes, and we expect the number of grapes to be lower than the average of the last few years, probably in line with last year's. Now we have to wait and hope for good rainfall because the vineyard cannot reach the harvest without rain. We hope for healthy, abundant rainfall, even staggered in two or three waves."
The effects of global warming are fast changing the geography of Italian farming.
A few years ago, olive trees and vines were mainly the preserve of hot and arid areas such as Sicily.
Now even Val d'Aosta in the very north, famous for its ski resorts and mountains, can produce its own oil, the farmers say.