Romania’s vineyards and the heat: where each grape can ripen, 1961 to today

1961–1970

Where Cabernet Sauvignon ripened in the 1960s#

Vine researchers measure a summer’s warmth with the Huglin index: for every day from April to September, the average of how far the mean and the maximum temperature rise above 10 °C, added up over the season. Each grape needs a certain sum to ripen. For Cabernet Sauvignon the published threshold is 1,900.

The colour on the map is the land where the sum passed 1,900 in at least 8 summers out of 10 between 1961 and 1970: the Danube plain, the Banat, Crișana, Dobruja and the foot of the lowest hills, 38% of the country. The line ran at about 160 m above sea level (its median height).

1971–1980

Then the line went down#

The 1970s had the coolest summers since 1961. In 1971–1980 the Cabernet Sauvignon line fell to 91 m. On the hills of Moldavia and Transylvania, summers warm enough became rarer than before.

The thin rose-grey line that stays on the map is the 1961–1970 limit.

1980 → 2025

From the 2000s, the line climbs fast#

+303 m from the 1960s to the last ten years

Scroll and the years go by. Until the 1990s the line stays about where it was in the 1960s. Then it climbs up the valleys and slopes, decade by decade; the old lines stay behind, thin.

In 2016–2025 Cabernet Sauvignon gets the heat it needs in 8 summers out of 10 on 69% of the country, and the line runs at about 463 m. Over today’s vineyards the Huglin index has risen by 350. That much heat is lost by climbing 278 m up a hill.

Five grapes

Each grape has its own line, and all of them climbed#

Grapes that need less heat ripen higher up. The thresholds, built on Pierre Huglin’s index, come from the Geisenheim research institute in Germany: Müller-Thurgau 1,500, Pinot noir 1,700, Merlot 1,800, Cabernet Sauvignon 1,900, Syrah 2,000. The environment agency of the German state of Hesse sets a higher bar for Merlot (1,900) and Syrah (2,100). The table below gives both.

Pick a grape above the map. With the Geisenheim thresholds, between the 1960s and the last ten years, every line climbed by 250 to 303 m. No threshold has been published for Romania’s own grapes: Fetească, Grasă, Băbească.

Cotnari

At Cotnari, the heat has passed Cabernet Sauvignon’s threshold#

Cotnari, in north-eastern Romania, is a white-wine vineyard: Grasă, Fetească albă, Tămâioasă, Frâncușă. Liviu Mihai Irimia and colleagues computed the Huglin index from the Cotnari weather station for 1951–1990 and 1991–2010: the vineyard stayed in the same class, moving from its lower edge to its upper edge. By a second index in the same study, Cotnari moved from a white-wine climate to a red-wine one.

This map, made from different data, gives a similar rise. Over the vineyards around Cotnari, 1951–1990: 1,876 (the study: 1,860.2); 1991–2010: 1,992 (the study: 2,024.2). The band with an index of 1,800–2,100 climbed on average from 148 to 183 m (the study: from 149 to 180 m); the 1,500–1,800 band from 333 to 373 m (the study: from 280 to 360 m). On the warmest quarter of the commune, the value reached in 8 summers out of 10 went from 1,856 in 1961–1970 to 2,252 in 2016–2025, past Cabernet Sauvignon’s threshold.

Târnave and Lechința

In Transylvania, Pinot noir climbs the hills#

Transylvania’s vineyards sit higher than those of the plains. In the 1960s Pinot noir (1,700) got the heat it needs in 8 summers out of 10 on 47% of the vineyards of central Transylvania, mostly in the valleys. In the last ten years, on almost all of them. On the warmest quarter of the town of Blaj, grapes up to Merlot ripened in the 1960s; now Cabernet Sauvignon and Syrah do too. At Lechința, only Müller-Thurgau and Pinot noir then; now Merlot, Cabernet Sauvignon and Syrah as well. For Blaj, a published study gives higher values; see below.

Maramureș and the high hills

Where nothing ripened in the 1960s#

In 1961–1970, in 434 of Romania’s 3,186 communes and towns, even the warmest quarter of the land did not gather, in 8 summers out of 10, the heat Müller-Thurgau needs, the least demanding of the five grapes. Today 149 remain, all in the mountains: in each, three quarters of the land lies above 600 m.

In the Maramureș basin, at Sighetu Marmației, the warmest quarter of the land barely passed 1,500 in the 1960s (1,552) and fell below it in the 1970s (1,433). In the last ten years it reached 1,910: Cabernet Sauvignon’s threshold.

The vineyards

The vineyards stayed where they were#

The cream dots are the vineyards on the European Union’s CORINE map of 2018. CORINE’s change maps, which record changes of 5 ha or more, find in Romania, between 1990 and 2018, 21,700 ha of vineyard lost and only 4,100 ha of new vineyard on land that had not been vineyard. Plots under 5 ha, old or new, escape them.

Romania has far fewer vines than in 1961: 306,300 ha then, 161,930 ha in 2024, according to the FAO. The vineyards that remain are on the same hills. Over them, the Huglin index went from 2,057 (1961–1970) to 2,407 (2016–2025).

What was planted

The grapes changed#

The 2015 vineyard survey (Eurostat) sorts vines by age and, for half of the area, by grape colour. Among vines over 30 years old, red grapes are 31.7%; among vines under 10, 44.8%. The smaller 2020 survey shows the same: 33.7% and 43.3%.

Of the Cabernet Sauvignon vines, 65.3% are under 10 years old; of Fetească neagră, 63.2%; of Syrah, 97.8%. Of Fetească albă, 7.9%; of Băbească neagră, 0.1%. But Pinot noir and Chardonnay, which need little heat, are also mostly young vines. The survey shows what was planted, not why.

How sure the map is

Tested on 108 weather stations it does not use#

The map starts from E-OBS, Europe’s measured daily temperatures on a 0.1° grid, and carries them onto 250 m squares along the relief. In Romania E-OBS uses 29 stations, 25 of them still reporting. Another 108 stations, 107 in Romania and one in the Republic of Moldova, from NOAA’s archive, are not in E-OBS; they are the test.

For 2016–2025 the map is off by at most 50 at half of them, about the difference made by 40 m of height. The mean error is 56 below 400 m and 82 above; the largest is at Mangalia, on the coast, where the sea breeze cools the summers. At the 9 stations that also have data for 1973–1990, the measured warming to 2016–2025 was 426; the map gives 418. A second dataset, ERA5-Land, shows the same warming from 1961–1990 to 1996–2025 at 26 points (286, against 280 on the map), though it runs about 164 cooler than the map.

For the 1960s no station outside E-OBS has records. At the E-OBS stations, the map is off in 1961–1970 by 42 on average per station and year, and ERA5-Land runs 143 cooler than the map then and 164 cooler now: the difference between the two datasets has changed little.

Southern England

Southern England first crossed the lowest threshold around 2000, and widely only since 2016#

Southern England sits far below Romania’s numbers. The same arithmetic on the same E-OBS grid, for England and Wales south of 52° N and east of 3.5° W: in 1961–1970 no square of that land reached an index of 1,500 even on its ten-year average; the warmest reached 1,294. In 2016–2025, 20.5% of it passed 1,500, most of it around London, and the warmest square reached 1,725.

England’s best-known vineyards are still just below it: the square around Nyetimber in West Sussex gives 1,486, the one around Chapel Down in Kent 1,443. In Romania, the same 1,500 has covered most of the plains and low hills since 1961.