Report by: Silvio Davison, Gian Marco Scarpa (CNR-ISMAR)
This report analyzes sea temperature trends for the first part of 2026 at the main exchange points between the lagoon and the sea along the Venetian coast, using sub-surface temperature time series measured at several CNR-ISMAR marine observation sites. Specifically, the observation sites examined are distributed across the three inlets of the Venice Lagoon (the Chioggia, Malamocco, San Nicolò, and Treporti stations) and at the Acqua Alta Oceanographic Platform (AAOT). The temperature data collected at these stations have a temporal resolution of 10 minutes and are recorded at a depth of two meters at the port inlets and three meters at AAOT. The analysis of the 2026 thermal anomaly uses the 2020–2025 period as a reference, for which time series are available at all the observation sites considered.
Starting with the coastal belt, Figure 1 shows the temperature trend at the Chioggia, Malamocco, San Nicolò, and Treporti stations during 2026 is compared to the reference period, represented by the mean (black line) and its interannual variability (grey band).
The comparison reveals a distinctive pattern for the month of January, with temperatures noticeably lower than the 2020–2025 reference at all four stations (monthly mean anomalies ranging between –1.81 and –1.14 °C). In the following months, by contrast, temperatures remained almost consistently above the reference period average, and with the onset of summer, heat waves became particularly evident due to the marked persistence of anomalous thermal conditions. Specifically, June shows monthly mean anomalies of roughly +0.85 to +1.42
°C, while in July these are positive but more contained (between +0.25 and +0.89 °C). The largest thermal anomaly, however, is observed in August (still ongoing at the time of writing), when the monthly mean anomaly relative to 2020–2025 reaches +2 °C at nearly all coastal stations (with the exception of Malamocco), confirming particularly intense warming especially in the two channels of the Lido inlet.
Moving toward the open sea, Figure 2 shows an analogous comparison for 2026 is shown for the Acqua Alta Oceanographic Platform, using the same representation for the reference period mean (black line) and its interannual variability (grey band).
At the Acqua Alta Oceanographic Platform, the seasonal pattern largely mirrors what was observed at the port inlets, albeit with some specific differences. Winter begins with temperatures roughly in line with the average of previous years, unlike the clearly negative signal recorded at the port inlets, before shifting rapidly to values higher than the 2020–2025 control period with the onset of spring. In particular, in April the water temperature shows a monthly mean deviation of about +2 °C compared to previous years, while the anomaly eases slightly in May. With the start of summer, the water temperature then undergoes several successive waves of intense warming. Notably, at the end of June and the beginning of August, the AAOT station recorded the highest daily mean temperatures of the year (so far), consistent with the pattern at the port inlets, with the maximum daily mean value of 29.9 °C recorded on August 6. For the month of August (still ongoing), the monthly mean deviation so far exceeds +1.5 °C relative to the reference period. To compare the thermal trend of 2026 with that of 2024 — another particularly notable year for temperature anomalies (also described in the 2024 AAOT bulletin: 10.26383/CNR-ISMAR.2025.2) — hourly sub-surface water temperature values for both years at AAOT were compared (inset of Figure 2). This comparison shows that, while the peak in daily means occurs in early August, the peak in hourly sub-surface temperature values for 2026 is observed at the end of June (30.60 °C on June 30 at 3:00 PM), and is slightly lower than the highest temperature recorded in 2024 (30.88 °C on August 13 at 5:00 PM).
In conclusion, observations conducted at all three port inlets (Chioggia, Malamocco, San Nicolò, and Treporti) and at the Acqua Alta Oceanographic Platform confirm 2026 as a particularly warm year for the waters of the northern Adriatic and the Venice Lagoon, with temperatures exceeding 30 °C on multiple occasions and at multiple stations. 2026 stands out especially for the early onset and persistence of the warm signal, with values significantly above the 2020–2025 average for nearly the entire duration of spring and summer, reaching monthly mean anomalies of over 1.5 °C offshore and over 2 °C along the coast in August.
