Venice floods between September and March, and most heavily in November. Of the 21 highest tides recorded at the Punta della Salute gauge since 1872, ten are November dates, six are December, three are October, one is February and one is April (ISPRA, 2026). Autumn is the season to plan around, and November sits at its centre.
What a visitor actually meets has changed since the MOSE barriers began operating in October 2020. In 2025 no tide reached 110 cm inside the historic centre while seven were measured out at sea, and the number of tide maxima at or above 80 cm, the level at which water starts to cover Piazza San Marco, fell to 161 from 227 in 2024 (ISPRA, 2026). Flooding in the city today usually means a few hours of shallow water on the lowest pavements rather than the depths of 1966 or November 2019.
This page is the calendar and the record: which months carry the risk, how many events a year cross each threshold, how long one lasts, which ground goes under first, and what to carry. The physics sits on the acqua alta science page, the barrier on the MOSE page, and the live numbers on the tide forecast page.
When does Venice flood?
The flood season is late autumn and winter. Barrier activations in Venice typically fall between October and February, matching the storm surge season in the northern Adriatic (Michielotto et al., 2026). The official closure log for the 2025/2026 season runs from 10 September 2025 to 15 May 2026, so the shoulders of that window are real (Autorità per la Laguna di Venezia, 2026).
Within the season, months are far from equal. In 2025 November carried the highest monthly mean sea level of the year, 48.1 cm above the local datum, and the most tide maxima at or above 80 cm, 26 of them, followed by March, August and October with 17 each. February recorded none at all, alongside the lowest monthly mean sea level of the year, because high pressure tends to settle over the region in that month (ISPRA, 2026).
The season has exceptions worth knowing about. The gates were raised in May and in late August 2023 (Michielotto et al., 2026), and the one tide at or above 110 cm measured inside the city in 2024 came on 16 May, the first since 2021 (ISPRA, 2025). A summer trip is very unlikely to meet acqua alta, though it is no longer impossible.
What time of year does Venice flood? The record, month by month
ISPRA keeps the list of the most significant acqua alta events at four lagoon gauges. For Punta della Salute, the station that represents the historic centre, the list holds 21 entries of 144 cm or more, measured against the Punta della Salute datum and updated to 31 December 2019 (ISPRA, 2026).
The months in that list are lopsided. Ten entries are November dates, six December, three October (two of them separate peaks on 29 October 2018), one February and one April. Sixteen of the 21, in other words, fall in November or December, and 19 of 21 between October and February.
The top of the list is familiar. The record is 194 cm on 4 November 1966, and the second highest is 189 cm on 12 November 2019 (ISPRA, 2026; Lionello et al., 2021). November 2019 was the worst month in the whole gauge record, with 15 events above 110 cm and four above 140 cm (Lionello et al., 2021). After those two come 166 cm on 22 December 1979, then 158 cm on 1 February 1986 and 156 cm shared by 1 December 2008, 29 October 2018 and 15 November 2019. The single outlier is 147 cm on 16 April 1936.
How often does Venice flood, decade by decade
Counting at the 110 cm threshold, which marks a severe high tide, gives the clearest trend. The average was 4.2 events per decade in the first half of the twentieth century (Lionello et al., 2021). It reached 52 events in 2000 to 2009 and 95 events in 2010 to 2019 (Michielotto et al., 2026). The 120 cm threshold tells the same story: fewer than two events per decade early in the century against 40 in 2010 to 2019 (Lionello et al., 2021). The single worst year in the series was 2019, with 28 cases above 110 cm (ISPRA, 2025).
The cause is the rising baseline rather than stormier weather. Mean sea level at Punta della Salute has risen by 2.6 mm per year since 1872 and by 4.6 mm per year over 1994 to 2025, and the reconstructed annual mean hit a series record of 41.1 cm above the datum in 2024 before easing to 37.4 cm in 2025 (ISPRA, 2026).
Since October 2020 the count inside the city and the count at sea have parted company. In 2024 the city saw one tide at or above 110 cm against 12 at sea, and in 2025 none against seven (ISPRA, 2025; ISPRA, 2026).
Does Venice flood in October?
Yes, though less often than in November or December. October holds three of the 21 highest tides on record at Punta della Salute: 156 cm and 148 cm as two peaks on 29 October 2018, and 145 cm on 15 October 1960 (ISPRA, 2026). In 2025, October produced 17 tide maxima at or above 80 cm, level with March and August and well behind November (ISPRA, 2026).
The barrier record says the same. In the 2025/2026 season the first closure of all three inlets came on the morning of 10 September 2025, with 111 cm recorded at the offshore platform, and by 5 October the gates were going up again (Autorità per la Laguna di Venezia, 2026).
The practical reading for an October trip is that one or two mornings of shallow water on the lowest pavements are plausible, deep flooding is not, and the forecast is worth a look the evening before. October and November are also the two months the site's month guides cover in more detail.
How long does acqua alta last, and which ground floods first
An acqua alta event is a tide peak, so it is measured in hours. Across the 69 barrier closures between 2020 and 2023, a closure lasted 8.6 hours on average, with a standard deviation of 6.4 hours, and the gates were up for 146.3 hours a year on average (Michielotto et al., 2026). The water drains as the tide falls. The exception that defines the extreme is 1966, when the level stayed above 110 cm for 22 hours (Lionello et al., 2021).
The lowest ground goes first, and that means Piazza San Marco. Water starts to cover the square at 80 cm above the Punta della Salute datum (ISPRA, 2026). The lowest areas of the square are already partly flooded at that level (Lionello et al., 2021). When the level reaches 110 cm, about 12 per cent of the city's area floods (Michielotto et al., 2026).
Local works have raised the floor under this. Banks and pavements in Venice have been raised to an average defence level of about 110 cm, with 100 km of banks reinforced and 13 km2 of defended area, and the Piazza San Marco works were designed to keep the square crossable up to 110 cm (Consorzio Venezia Nuova, 2026).
What to pack and what to do when the water comes up
Waterproof footwear with a high enough shaft is the whole kit. Boots are sold all over the city when the forecast turns, and disposable plastic overshoes tear quickly. The water is cold, dirty lagoon water, so bare feet and canvas shoes are a poor plan.
Read the number, not the headline. Anything forecast below 80 cm leaves the pavements dry, because that is the level at which Piazza San Marco starts to flood (ISPRA, 2026). Between 80 and 110 cm the lowest routes are wet and the rest of the city is normal. Above 110 cm roughly an eighth of the city is affected, which is when the city sets out its raised walkways on main pedestrian routes (Michielotto et al., 2026).
The sensible adjustments are small. Move a San Marco visit to the other half of the day, keep museum and church visits for the peak hour, and expect waterbus stops near the lowest ground to be awkward for an hour or two. Shops and cafes in the affected lanes stay open with their own barriers at the door.
How far ahead is a Venice flood forecast worth trusting?
Far enough to plan a day, not far enough to plan a trip. The forecast error that matters runs in both directions. On 12 November 2019 every available forecast system underestimated the peak, by as much as 45 cm, and the city was flooded again on 8 December 2020 after another forecast failure (Lionello et al., 2021).
The opposite error is now more common. The predicted maxima issued by the municipal alert system before each barrier closure have often been well above what was then measured in the city, and that precautionary margin is a large part of why the gates go up as often as they do, though the gap has been narrowing over time (Michielotto et al., 2026).
For a visitor the useful horizon is short. A forecast several days out is a statement about the season, while the bulletin for the next tide cycle is the number to act on. The site's tide forecast page carries where to read it, and the forecast accuracy page covers how much each horizon is worth in centimetres.
