THE WIND
The bora, the wind that gives the race its name
The katabatic wind that sculpts the Karst and gives its name to an entire event.
The bora is the wind that gives the Corsa della Bora its name: it blows over the Karst and the Gulf of Trieste, mainly in winter, right on race weekend. This page explains what it is, when and how hard it blows, what the regulations say about running safely when it is blowing, and why it has become the name of a whole running event.
What is the bora?
The bora is a wind that is katabatic: a cold, dense air mass of continental origin that builds up on the Karst plateau and, once the difference in pressure and density with the milder air below becomes great enough, plunges towards the Adriatic Sea, channelled through the passes of the Dinaric Alps. The main pass from which the bora that hits the Gulf of Trieste originates is Postumia/Postojna (Slovenia), between the Nanos plateau and the Snežnik/Nevoso massif: a gap that acts as a funnel and sharply accelerates the airflow on its way down.
The phenomenon is typical of the northern Adriatic, but it reaches its greatest intensity and fame in Trieste: the city is hemmed in between a relatively warm sea and a high, cold Karst hinterland, with a pass opening right onto the gulf. The name comes from Boreas, the north wind of Greek mythology. It is an intermittent wind, not a steady flow: it blows in gusts of varying strength (“refoli” in the Triestine dialect), carried by a relatively shallow layer of cold air, between 400 and 800 metres thick — which is why, in some places, the sky can stay clear above the bora while the wind at ground level is already very strong.
When does it blow, and how hard?
The bora is a phenomenon that occurs mainly in winter, although it can also occur in other seasons. An Istrian proverb sums up its typical duration well: “Three days it is born, three days it grows, three days it dies” — it starts, strengthens and blows itself out in cycles of about three days.
In the ten years of weather statistics collected by the organisation for the editions of the Corsa della Bora (the page called Weather), the race weekend — always in January — has historically been split between the bora (55% of editions) and the sirocco, the warm, humid wind from the south-east (45%): a figure that confirms how structurally exposed the period chosen for the race is to the phenomenon, without meaning that the bora is guaranteed every year.
Over the years, weather stations in Trieste have recorded some of the strongest gusts in the Mediterranean, with readings that vary with the anemometer and how exposed it is: 171 km/h in 1954 at the Thalassographic Institute — the gust that broke the measuring instrument, still cited as the best-known “historical” record; 188 km/h on 10 March 2010 (anemometer at the Nautical Institute); 182.88 km/h on 11 February 2012 (ISMAR anemometer, Fratelli Bandiera pier). There is no single, authoritative “official record”: the figure depends on where and with what instrument it is taken, and the 1954 reading remains the most quoted because of its historical fame.
The verified race-day figure is that of the edition 2021 of the Corsa della Bora, run in the thick of a full-blown bora: 130 km/h gusts, with air temperatures between 0° and 6° and a perceived temperature below zero — the only figure the organisation declares for one of its own editions, published on the page called Weather.
Running in the bora: race experience and safety
The bora is part of the race experience, not a hidden obstacle. On the S1 TransKarst Ultra you feel it as real terrain: a bigger, more intense experience, with more of a story to tell by the time you finish. On the Monte Ermada loop, shared by several distances — from the S1 Half Trail upwards — you run along ridge sections where the bora blows unobstructed and the view sweeps from the Julian Alps to Istria. On clear bora days, the same air that makes the running harder also gives the best visibility.
Safety does not rest on storytelling, but on the Official Regulations.Article 7 (Equipment) requires every competitor to carry, for the entire duration of the race, the mandatory kit listed on the page for their distance — with the explicit instruction not to choose the lightest possible clothing, but clothing that offers adequate protection in the mountains against adverse conditions (cold, wind, driving rain and snow). For the longer and more exposed distances, the mandatory kit includes a thermal blanket, gloves, a hat, a windproof jacket, trousers and a long-sleeved top, and a head torch: not a mere formality, but the minimum kit needed to cross the most exposed stretches of the Karst safely.
TheArticle 24 (Exceptional conditions) provides that the organisation reserves the right to change courses, start times, time barriers and the position of checkpoints and refreshment points at any time; in cases of force majeure or conditions that could jeopardise the safety of participants, it may also delay the start, adapt the course, or cancel or stop a race that is already under way.
The bora in the Corsa della Bora
The “S1” in the name of every distance (S1 Borin, S1 Half Trail, S1 TransKarst Ultra…) stands for Sentiero 1, the CAI trail that the race follows for much of its course — as defined by the Official Regulations. “Bora” is not a decorative addition: it is the wind that “sculpts the Karst, that pushes you or stops you, that makes every metre different from the one before”. The motto that accompanies the Rilke Path — “Being here is wonderful” — is taken from the Duino Elegies by Rainer Maria Rilke, the poet who stayed at Duino Castle on these same bora-swept coasts: the same wind that makes the race harder is part of what makes being there “wonderful”.
Two points on the course stand out as objectively more exposed to the bora when the published race descriptions are cross-checked against independent external sources. In Val Rosandra/Dolina Glinščice, at km 13.2 (Bagnoli della Rosandra/Boljunec refreshment point) — a stretch shared by S1 Trieste Ultra and S1 Bora Ultra — lies the Sella della Bora, the point in the province of Trieste where the wind reaches its highest speeds: the two night races therefore cross, in their first hours of running, one of the most exposed stretches in the whole area. The second stretch is theMonte Ermada loop, followed by the S1 Half Trail and shared with Borderless and TransKarst: a ridge where the bora blows unobstructed.
In 2027 the Corsa della Bora reaches its 12th edition: every year the courses are renewed, but the wind remains the only constant from one edition to the next.
Cultural curiosities
Meteorologists distinguish between two types of bora. The clear bora (anticyclonic) is associated with clear skies, very dry air and exceptional visibility, and is driven by a well-developed anticyclone over central and eastern Europe. The dark bora (cyclonic) brings, by contrast, overcast skies, rain or snow, when cold air flows beneath moister, more unstable air masses brought in by a low-pressure system over the Adriatic. The difference is not one of intensity but of the surrounding conditions: as an air mass, the bora is only a few hundred metres deep, so above it the sky may stay clear or be covered by sirocco clouds.
There is no specific “bora scale” recognised internationally: wind strength is measured on the standard Beaufort scale, the same one used for any other wind. Locally, the Civil Protection of Friuli Venezia Giulia issues strong-wind warnings with colour-coded alert levels (yellow, orange, red) when the forecasts point to hazardous conditions.
In Trieste there is a street named after the wind itself: according to the local historian Antonio Tribel (1884), it took its name because the bora, when it blows, “hinders pedestrians’ passage more along this street than along any other” — the wind funnels between the narrow walls of the street, increasing in intensity. The street is now a stop on theBora Itinerary of the TriesteMetro project. In the most exposed parts of the city, ropes or iron handles used to be fixed to the walls of houses, which pedestrians could grab to keep walking against the wind — a practical measure that became part of the city’s collective imagery of the bora. Trieste is also home to the Bora Museum — The Warehouse of the Winds, which opened in 2004 and has grown over the years into a multi-site museum, with new spaces in Opicina/Opčine.
In the Triestine dialect dictionary, “borin” is the word for a light bora, a brief gust — a curious semantic coincidence with the name of the race’s shortest distance, the S1 Borin (5.5 km), although none of the sources consulted explicitly states this as the origin of the race’s name: we flag it as a curiosity, not as a confirmed fact.
For the full, binding details of the mandatory kit and safety clauses for each distance: Regulations page. For the edition-by-edition weather history: Weather page.
Frequently asked questions about the bora
What is the bora?
The bora is a katabatic wind: cold, dense air of continental origin builds up on the Karst plateau and plunges towards the Adriatic through the passes of the Dinaric Alps. The main pass for the Gulf of Trieste is Postumia/Postojna, between the Nanos plateau and the Snežnik massif: it works like a funnel and sharply accelerates the downslope flow.
Where does the bora blow from?
From the Karst plateau down to the sea. Cold continental air spills over the Dinaric Alps and is funnelled through the Postumia/Postojna pass, in Slovenia, between Nanos and Snežnik: from there it drops down towards the Gulf of Trieste, and the narrow gap makes it pick up speed.
When does the bora blow in Trieste?
Mostly in winter, though it can occur in any season, and it comes in cycles of about three days, as the Istrian proverb says: “three days it is born, three days it grows, three days it dies”. In the ten years of statistics collected for the Corsa della Bora, the January race weekend has had bora in 55% of editions and sirocco in 45%.
What kind of wind is the bora?
It is a cold, dry fall wind, and meteorologists distinguish two types: the clear bora, anticyclonic, with cloudless skies, very dry air and exceptional visibility; and the dark bora, cyclonic, with overcast skies, rain or snow. The difference lies not in the intensity but in the surrounding conditions: as an air mass, the bora is only a few hundred metres deep.
How strong does the bora get?
The weather stations in Trieste have recorded some of the strongest gusts in the Mediterranean: 171 km/h in 1954 at the Thalassographic Institute, 188 km/h on 10 March 2010, 182.88 km/h on 11 February 2012. There is no single official record, because the reading depends on the anemometer and on how exposed it is. For the race itself, the verified figure comes from the 2021 edition, run in gusts of 130 km/h.
What is the wind in Trieste called?
It is called the bora. In Trieste the wind has a street named after it: according to the historian Antonio Tribel, the street took its name because the bora “hinders pedestrians’ passage more along this street than along any other”. In the most exposed spots, ropes and iron grab handles were fixed to the walls of the houses for people to hold on to, and the city is home to the Bora Museum.