From accumulation to melt: March changes the course of the snow season

March 13, 2026

March has arrived bringing milder air and clearer skies. For the snow water resource this marks a transition phase: the snow accumulated during winter begins to gradually melt, feeding rivers, lakes and downstream ecosystems.

At the national scale, after the strong improvement observed between January and February, Italy enters this new phase still with a slight deficit in Snow Water Equivalent (SWE), equal to –22%. The season has therefore changed pace, entering the phase following what we call the “peak snow accumulation”: the period when accumulation gives way to melt.

Looking at the seasonal evolution, the dynamics resemble something of a roller coaster. After the progressive growth of the snowpack until mid-February, the curve reached its peak, more or less in line with what climatology would expect, and has since begun to decline. Melt is now proceeding rapidly.

Fig. 1. Evolution of snow water equivalent in Italy. The orange line represents the snow water equivalent for the current season, aggregated over the entire national territory. The light blue line represents the total snow water equivalent for the previous season, while the grey line and shaded area indicate, respectively, the long-term average and interannual variability.

The Italian Alps: peak reached and early melt

The pattern becomes evident when observing the Italian Alpine arc as a whole. During February, accumulation even exceeded the seasonal average, but the peak has now been surpassed and the decline has begun earlier than climatology would suggest.

The melt phase appears to be occurring about one month earlier than the typical pattern observed in the historical record. Overall, the Italian Alps now stand at approximately –12% compared to the seasonal average.

This transition from accumulation to melt is a natural phase of the snow cycle, but this year it appears to be happening more rapidly than usual, as has increasingly occurred in recent years.

Fig. 2. Integrated Snow Water Equivalent evolution across the Italian Alps. The orange line represents the snow water equivalent for the current season, aggregated over the entire national territory. The light blue line represents the total snow water equivalent for the previous season, while the grey line and shaded area indicate, respectively, the long-term average and interannual variability.

Apennines: an even sharper descent

The dynamics are even more pronounced along the Apennine range. Here the seasonal peak was reached in early February, as often happens, and the melt phase has already been underway for several weeks.

After remaining within the range of “normal” seasonal variability for much of the winter, the Apennines now show a very marked deficit of –73%. The downward part of the snow “roller coaster” began earlier and is proving more rapid.

Fig. 3. Integrated Snow Water Equivalent evolution across the Italian Apennines. The orange line represents the SWE for the current season; the light blue line represents last season; the grey line and shaded band indicate the historical mean and interannual variability.

The role of temperature and precipitation

The main cause of this acceleration lies in the meteorological conditions observed in February. The month was significantly warmer than average across the entire Italian territory. Even though temperatures over the December–February winter period were slightly below average at higher elevations, a single very warm month is sufficient to trigger an early onset of snowmelt.

Another factor must also be considered: in some Alpine areas precipitation has been scarce. In particular, the Triveneto region recorded winter precipitation deficits reaching up to –60%, further reducing the available snow accumulation.

Fig. 4. Temperature anomaly in Italy for February and the December–February period.

Fig. 5. Precipitation anomaly in Italy for February and the December–February period.

The result is a combination well known to snow scientists: less snowfall and higher temperatures, conditions that favor early melt and quickly bring the system back into deficit.

River basins under observation: Adige, Tiber and Po

Fig. 6. Snow Water Equivalent (SWE) values observed on March 7 across the monitored river basins for each year from 2011 to 2026.

Among the Italian basins most closely monitored for snow resources is the Adige basin, which remains below average with a deficit of approximately –26%. Here too the seasonal peak appears to have been reached and melt has begun, with conditions very similar to those observed at the same time last season.

A comparable dynamic emerges in the Tiber basin, where melt began already at the beginning of February. In this case the pace of the decline is similar to previous years, but the starting point is different: winter reached February with roughly half the snow that was typical in the past.

The most positive picture remains that of the Po basin, where the peak also appears to have been reached but conditions remain close to the seasonal average (–2%). Compared with last year, north-western Italy experienced a winter that was more similar to what historically characterized these regions, at least at higher elevations.

Fig. 7. Trend of snow water equivalent in the Adige River basin. The orange line represents the snow water equivalent for the current season, aggregated over the entire national territory. The light blue line represents the total snow water equivalent for the previous season, while the grey line and shaded area indicate, respectively, the long-term average and interannual variability.

Fig. 8. Trend of snow water equivalent in the Tiber River basin. The orange line represents the snow water equivalent for the current season, aggregated over the entire national territory. The light blue line represents the total snow water equivalent for the previous season, while the grey line and shaded area indicate, respectively, the long-term average and interannual variability.

Fig. 9. Trend of snow water equivalent in the Po River basin. The orange line represents the snow water equivalent for the current season, aggregated over the entire national territory. The light blue line represents the total snow water equivalent for the previous season, while the grey line and shaded area indicate, respectively, the long-term average and interannual variability.

When snow becomes water

Spring also marks a profound transformation of the snowpack.

“The spring months are always a delicate phase for snow water resources. Snow begins to melt starting from the lower elevations and gradually ‘retreats’ toward higher altitudes. It is a natural process, but when melt begins too early it can reduce the amount of water that will remain available during the warmer months,” explains Francesco Avanzi, snow hydrology researcher at CIMA Research Foundation.

SWE ANOMALY BY ELEVATION PO march — Fig. 10. Snow water equivalent (SWE) anomaly, represented by one point every 100 metres of elevation, highlighting the elevational distribution of the deficit across the Po River basin.

SWE ANOMALY BY ELEVATION ADIGE MARCH — Fig. 11. Snow water equivalent (SWE) anomaly, represented by one point every 100 metres of elevation, highlighting the elevational distribution of the deficit across the Adige River basin.

Melt does not occur uniformly. The water forming inside the snowpack infiltrates and flows along slopes and hillsides, creating preferential flow paths.

“With the entry of water into the snowpack,” Avanzi continues, “the structure of the snow itself changes: crystals become rounded, grains grow larger, and the snow progressively becomes wetter.”

This process is known as wet-snow metamorphism, the transformation through which the snow accumulated during winter gradually turns into water feeding rivers and reservoirs.

Fig. 12. Snow grains before (left) and after (right) wet-snow metamorphism (source: F. Avanzi and M. Schneebeli, SLF Davos). As temperatures increase, liquid water enters the snowpack and progressively rounds the crystals, altering their shape and size: the original structure, which still vaguely resembles that of snowflakes, gradually transforms into more rounded and coarser grains. (The scale bar is in tenths of a millimetre).

What to expect in the coming months

Looking ahead, seasonal forecasts provided by ItaliaMeteo indicate temperatures above the climatological average, especially during March.

anomalia temperatura 2026 03 p50 — Fig. 13. Forecast of average temperature anomalies for March 2026 relative to the climatological average (source: ItaliaMeteo).

anomalia temperatura 2026 AMG p50 — Fig. 14. Forecast of average temperature anomalies for the quarter April/May/June 2026 relative to the climatological average (source: ItaliaMeteo).

On the precipitation side, forecasts suggest that March may be drier than normal in Italian mountain areas, with a possible return to wetter conditions during the April–June period.

anomalia precipitazione 2026 03 p50 — Fig. 15. Forecast of total precipitation anomalies for March 2026 relative to the climatological average (source: ItaliaMeteo).

anomalia precipitazione 2026 AMG p50 — Fig. 16. Forecast of total precipitation anomaly for the quarter April/May/June 2026 relative to the climatological average (source: ItaliaMeteo).

These are not ideal conditions for maintaining the snow resource: the meteorological context appears more likely to favor continued melting rather than late-season snowfall.

Toward the decisive phase of the season

The snow season has now passed its point of maximum accumulation. The peak lies behind us and the downward phase has begun.

The key question is no longer only how much snow will fall, but how quickly the existing snow will turn into water. It is during this phase that the real impact of snow on spring and summer water availability is determined.

The next update, scheduled for mid-April, will help clarify how much of this snow will ultimately reach rivers and reservoirs across the country.