The Bora, measured

'How strong is it? How many days a year? In summer too? And where?' These are the Bora questions buyers ask us most often, especially those who come from abroad and know it only by reputation. People born in Trieste usually answer with a story. The stories are true, but choosing a home takes numbers.

For every home we offer we measure what can be measured: how many hours of sun the terrace gets, how high it stands, how warm the sea is below the house. This page does the same with the wind. It sets out what can honestly be said about Trieste's Bora, with numbers from weather stations, satellites and terrain, and the sources at the bottom. It also says what is not known.

We are not a weather service and do not want to look like one. The data come from the Friuli Venezia Giulia environmental agency (ARPA) and Civil Protection, from Italy's National Institute of Oceanography and Applied Geophysics (OGS), from the American NOAA and from the European Copernicus programme;^1,2,4,29,30 the calculations are ours, and anyone can repeat them. We do it because anyone buying a home, from Trieste or from Vienna, should be able to see all the data that exist, not just the photographs.

The first two figures come from the Trieste synoptic station in the years when it measured consistently, 2006-2011 and 2013-2014; the other two from ARPA at the Molo F.lli Bandiera, since 1994.^2,3,12 The Bora blows all year round, more from October to March and less in May and June; when the wind in Trieste goes above 18 km/h, 91 times out of a hundred it is the Bora.² How much of it arrives depends a great deal on the place: in the 49 Bora episodes between September 2025 and October 2026, winter included, the Karst plateau had between 45 and 66% of the Molo's mean wind, the buoy in the middle of the gulf 101%.²⁹

• The Bora calendar comes from a single station, Trieste's, and from eight years in which it measured consistently; it is not the climate of the whole province, and it does not say whether the Bora is changing.^2,3
• The comparison between stations comes from 49 episodes between September 2025 and October 2026, 19 of them in winter: it is a single year, and another year may give somewhat different ratios.^8,29
• Satellites see the wind over the sea, not on land.^5,6
• The buoy off Miramare measures on the water: its ratio to the Molo is a clue for the coast road, not the wind on land.³⁰
• Gusts cannot be compared between different instruments, nor at the Molo before and after 2005, when ARPA changed how it measures them.¹²
• The terrain is the 30-metre Copernicus model: buildings and trees are included, smaller details are not.⁴
• Every calculation can be repeated: the programs and downloaded data are kept, and we send them to anyone who asks.

1. 1.
   Note 1. ARPA FVG - OSMER e GRN, weather stations around Trieste: hourly mean wind, hourly maximum wind and direction from 1 August to 23 October 2026, read from the station charts page on 23-24/10/2026 (CC BY-SA 3.0 IT licence). These readings are the source of 8 August 2026 hour by hour, in the 3D view at the top of the page and in its chapter: TriesteVillas processing. meteo.fvg.it ↗ (opens in a new tab) · accessed 24/10/2026↩abc
2. 2.
   Note 2. TRIESTE synoptic station (WMO 16110, ICAO LIVT), hourly METAR and SYNOP observations in NOAA's Integrated Surface Database (public domain), data from 1932 to 2025. For the figures on this page, the years 2006-2011 and 2013-2014: one observation every hour, calms and gusts recorded the same way. Bora = wind from 40-100° (north-east to east); Bora day = at least three such hours above 18 km/h (5 m/s); gust = the gust reported in the bulletin or, if missing, the mean wind. TriesteVillas processing. ncei.noaa.gov ↗ (opens in a new tab) · accessed 24/10/2026↩abcdefghijk
3. 3.
   Note 3. The Trieste series is not homogeneous: calm hours are about 45% in the 1990s, 5% in 2002, back to 30% in 2015-2017 and gone from 2023; 1972, 2005 and 2012 are missing. These are changes of instruments or recording, not of climate. That is why we use it for months, hours and durations, not to say whether the Bora is increasing or decreasing. TriesteVillas calculation on the same series as note 2.↩ab
4. 4.
   Note 4. Copernicus DEM GLO-30, 30 m digital surface model (tile N45 E013), © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA. It is a surface model: it includes buildings and trees. Cross-section along 68° through the Molo F.lli Bandiera: TriesteVillas processing. dataspace.copernicus.eu ↗ (opens in a new tab) · accessed 24/10/2026↩abc
5. 5.
   Note 5. R. P. Signell, J. W. Chiggiato, J. Horstmann, J. D. Doyle, J. Pullen, F. Askari, 'High-resolution mapping of Bora winds in the northern Adriatic Sea using synthetic aperture radar', Journal of Geophysical Research 115 (2010), C04020. RADARSAT radar winds on six Bora days in January-February 2003; the ratios for each stretch of coast are our reading of the colours of figure 10. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩abcdef
6. 6.
   Note 6. Sentinel-1: radar images of 44 strong-Bora days between 2014 and 2026 (at the Trieste station, at the time of the pass, direction 30-100° and mean wind of at least 8 m/s or gusts of at least 15 m/s), from the public Microsoft Planetary Computer catalogue; 10 m wind from the CMOD5.N model; sea cells 1 to 3 km from the shore, downwind, compared with the same off the Molo F.lli Bandiera. TriesteVillas processing, October 2026; the comparison holds for strong Bora. Contains modified Copernicus Sentinel data [2014-2026]. planetarycomputer.microsoft.com ↗ (opens in a new tab) · accessed 24/10/2026↩abcdefg
7. 7.
   Note 7. Episode, in the Trieste series: consecutive hours of Bora above 18 km/h, with gaps of two hours at most, and at least three hours in all. TriesteVillas calculation on the years in note 2.↩
8. 8.
   Note 8. Episode, at the Molo F.lli Bandiera: hours with wind from 40-100° and hourly mean wind of at least 20 km/h, with gaps of 2 hours at most, at least 6 hours and a gust of at least 60 km/h. Hours are built from the quarter-hours in note 29, at least three per hour: the mean wind is their average, the gust the strongest of them. A station enters the comparison for an episode if it has wind data for at least three quarters of its hours. TriesteVillas calculation on the data in note 29.↩abcd
9. 9.
   Note 9. B. Grisogono, D. Belušić, 'A review of recent advances in understanding the meso- and microscale properties of the severe Bora wind', Tellus A 61 (2009), 1-16: the weather patterns that produce it, the downslope windstorm driven by breaking mountain waves, the two arguments against gravity alone, the low-level jet at about half a kilometre, clear and dark Bora. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩abcd
10. 10.
    Note 10. D. Belušić, M. Pasarić, M. Orlić, 'Quasi-periodic bora gusts related to the structure of the troposphere', Quarterly Journal of the Royal Meteorological Society 130 (2004), 1103-1121: one-second measurements at Senj, December 2001 - January 2002, quasi-periodic gusts between 3 and 11 minutes. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩
11. 11.
    Note 11. C. E. Dorman and others, 'February 2003 marine atmospheric conditions and the bora over the northern Adriatic', Journal of Geophysical Research: Oceans 111 (2006): the strongest winds are concentrated in four jets steered by topography; the strongest is the Senj jet, the Trieste jet crosses the whole northern Adriatic, and between jets the wind is weak. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩
12. 12.
    Note 12. ARPA FVG - OSMER e GRN, climatological tables for the Trieste molo F.lli Bandiera station, 1994-2026, updated 5 October 2026 (CC BY-SA 3.0 IT licence): wind at 10 m, monthly maximum wind speed with its direction, days with daily gust above 15, 20 and 25 m/s, days with daily mean wind above 10 m/s, return periods calculated by ARPA. In 2005 ARPA changed how the maximum gust is sampled: gust counts cannot be compared before and after. The shares of Bora months (318 of 381 monthly maxima, 119 of the 130 months with a maximum of 100 km/h or more) and the 1996-2005 / 2006-2025 comparison are TriesteVillas calculations on the same tables. meteo.fvg.it ↗ (opens in a new tab) · accessed 24/10/2026↩abcdefghij
13. 13.
    Note 13. ARPA FVG - OSMER e GRN, Meteo FVG Report 2/2012 (February 2012), 'Event of the month': fifteen consecutive days of gusts above 100 km/h at the Molo F.lli Bandiera from 29 January to 12 February 2012, the 168 km/h gust of 11 February, seven ice days in Trieste during the month. meteo.fvg.it ↗ (opens in a new tab) · accessed 24/10/2026↩abcd
14. 14.
    Note 14. F. Stravisi, S. Cirilli, Dati meteorologici di Trieste, anno 2010, Rapporti OM no. 143, University of Trieste (2011): station of the Department of Geosciences on the roof terrace of the Nautical Institute; March 2010 maximum, 52 m/s from the north-east. arts.units.it ↗ (opens in a new tab) · accessed 24/10/2026↩
15. 15.
    Note 15. ARPA FVG - OSMER e GRN, Il vento in Friuli Venezia Giulia. Schede climatiche (2023), 'Trieste coast and Karst': in Trieste, 2001-2020, mean wind at 10 m of 14 km/h; wind from the north-east 16% of hours, averaging 29 km/h; episodes with an hourly mean above 35 km/h for more than five hours in a row are not rare. meteo.fvg.it ↗ (opens in a new tab) · accessed 24/10/2026↩
16. 16.
    Note 16. ARPA FVG, Il clima del Friuli Venezia Giulia (popular booklet, 2020), pp. 2 and 22: in the city the Bora reaches its greatest strength and persistence, more than on the plateau; it is less present around Muggia; the Karst has the lowest mean annual humidity in the region; north-easterly winds bring fine weather. arpa.fvg.it ↗ (opens in a new tab) · accessed 24/10/2026↩
17. 17.
    Note 17. F. Stravisi, 'Climatic variations at Trieste during the last century', Geofizika 4 (1987), 61-76: wind from north-north-east to east, at any speed, in 1903-1985 for 41.9 ± 5.6% of the time, i.e. 153 ± 21 equivalent days a year; a decline of 0.28 days a year per year, with an oscillation of about fifty years peaking around 1940. ojs.srce.hr ↗ (opens in a new tab) · accessed 24/10/2026↩
18. 18.
    Note 18. A. Belušić Vozila and others, 'Wind over the Adriatic region in CORDEX climate change scenarios', Journal of Geophysical Research: Atmospheres 124 (2019), 110-130: in the 21st century fewer winter Bora episodes in the northern Adriatic and more sirocco; wind speed during the Bora does not decrease; the signal depends strongly on the global model. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩
19. 19.
    Note 19. C. Denamiel, I. Tojčić, I. Vilibić, 'Far future climate (2060-2100) of the northern Adriatic air-sea heat transfers associated with extreme bora events', Climate Dynamics 55 (2020), 3043-3066: 22 extreme Bora events simulated for the end of the century, with wind up to 3 m/s weaker. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩
20. 20.
    Note 20. ARPA FVG - OSMER e GRN, Meteo FVG Report 6/2024 (June 2024), table of the daily mean sea temperature in Trieste at 2 m: 25.5 °C on 22 June, 22.5 on the 23rd, 19.1 on the 24th, 26.8 on the 30th. meteo.fvg.it ↗ (opens in a new tab) · accessed 24/10/2026↩
21. 21.
    Note 21. F. Raicich and others, 'Extreme air-sea interactions in the Gulf of Trieste (North Adriatic) during the strong Bora event in winter 2012', Journal of Geophysical Research: Oceans 118 (2013), 5238-5250: daily mean heat losses above 1,000 W/m², bottom water at 4 °C, density anomaly of 30.58 kg/m³, more than in 1929. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩
22. 22.
    Note 22. H. Mihanović and others, 'Exceptional dense water formation on the Adriatic shelf in the winter of 2012', Ocean Science 9 (2013), 561-572: record densities above 30 kg/m³ on the Adriatic shelf. doi.org ↗ (opens in a new tab) · accessed 24/10/2026↩
23. 23.
    Note 23. ARPA FVG, 'Aria sostanzialmente buona in Friuli Venezia Giulia', Ecoscienza 3/2020: in winter 2019-2020 pollutants stagnated in almost the whole region, except in the Gulf of Trieste, ventilated by the Bora and easterly winds. arpae.it ↗ (opens in a new tab) · accessed 24/10/2026↩
24. 24.
    Note 24. NOAA National Weather Service, 'Wind Chill Chart': the wind chill formula, valid below 10 °C with wind measured at 10 m. With 0 °C and a 50 km/h mean wind it gives about −8 °C: TriesteVillas calculation. weather.gov ↗ (opens in a new tab) · accessed 24/10/2026↩
25. 25.
    Note 25. Ministerial Decree of 17 January 2018, updated Technical Standards for Construction, Official Gazette no. 42 of 20 February 2018, ord. suppl. no. 8, §3.3.1, table 3.3.I: zone 8, province of Trieste, basic reference wind speed 30 m/s; zone 1, the rest of Friuli Venezia Giulia, 25 m/s. It is a 10-minute mean at 10 m with a 50-year return period. The 44% higher pressure is (30/25)², TriesteVillas calculation with the formula in §3.3.6. gazzettaufficiale.it ↗ (opens in a new tab) · accessed 24/10/2026↩
26. 26.
    Note 26. Italian Civil Protection Department, 'In caso di venti e mareggiate' (sheet republished by the Prefecture): secure objects exposed to the wind, such as pots on balconies and window sills, aerials and roof coverings; take care with structures made of fabric; avoid standing under trees and scaffolding, since broken branches are the most frequent injury. prefettura.interno.gov.it ↗ (opens in a new tab) · accessed 24/10/2026↩
27. 27.
    Note 27. ARPA FVG - OSMER e GRN, 'Il tempo meteorologico durante la Barcolana: anni 1994-2021', Trieste molo F.lli Bandiera station: in 2020 the regatta was called off because of bad weather, with strong Bora and rain. snpambiente.it ↗ (opens in a new tab) · accessed 24/10/2026↩
28. 28.
    Note 28. Museo della Bora (Bora Museum): the association and the Borarium at Via Nazionale 49 in Opicina, visits by appointment. museobora.org ↗ (opens in a new tab) · accessed 24/10/2026↩
29. 29.
    Note 29. Source: Protezione Civile della Regione Friuli Venezia Giulia (Civil Protection of the Friuli Venezia Giulia Region), weather monitoring data (CC BY 4.0 licence): mean wind, gust and direction every fifteen minutes, since 20 September 2025, from the stations of the regional network, the same as in note 1. Over the 31 hours of 8 August 2026 the gusts match those on ARPA's page and the mean wind differs by at most 0.7 km/h, at all fourteen stations. Data processed by TriesteVillas and kept in its archive, which updates itself every half hour: for each episode and each station, mean wind and strongest gust over the same hours, relative to the Molo; for each station, the median of the episodes, and in the figure the middle 80%. Winter: the episodes that began between November and March. The stations are not all at the same height above ground nor in the same kind of place. monitor.protezionecivile.fvg.it ↗ (opens in a new tab) · accessed 25/10/2026↩abcdefghijklm
30. 30.
    Note 30. OGS - National Institute of Oceanography and Applied Geophysics, MAMBO1 buoy in the Gulf of Trieste off Miramare (45.698 N, 13.708 E): mean wind, gust and direction hour by hour since October 2023, from the OGS ERDDAP server. These data were collected and made freely available by the Copernicus project and the programmes that contribute to it. Values flagged by quality control as probably bad, bad or missing are excluded. The anemometer is on the buoy, closer to the water than the Molo's ten metres. Ratios to the Molo of note 29, over the same hours and by the same rules: TriesteVillas processing. nodc.ogs.it ↗ (opens in a new tab) · accessed 25/10/2026↩abcdefgh