DOI: 10.25923/11nn-hn03

M. C. Serreze¹, S. Bigalke², R. Lader³, A. Crawford⁴, and T. J. Ballinger³

¹National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
²Department of Geography, Portland State University, Portland, OR, USA
³International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, USA
⁴Department of Environment and Geography, University of Manitoba, Winnipeg, MB, Canada

Headlines

• Precipitation averaged across the Arctic for water year 2024/25 (October 2024-September 2025) was at a record high, and precipitation totals for the winter, spring, and autumn seasons were each in the top five highest, reinforcing positive trends in Arctic precipitation over the 1950-2025 period.
• Summer was unusually dry, notably over parts of Eurasia and Canada.
• An intensifying water cycle with more extreme precipitation events threatens to further disrupt Arctic ecosystems, infrastructure, and communities.

Introduction

Annual precipitation over the Arctic region, taken here as poleward of 60° N, is characterized by high totals over the Atlantic sector due to open water and the frequent passage of storm systems, locally exceeding 2000 mm, and generally dry conditions elsewhere. Polar desert, with annual precipitation of 250 mm or less, characterizes much of the Canadian Arctic Archipelago and central Arctic Ocean, reflecting cold conditions and distance from moisture sources. However, within these patterns, there is strong seasonality and local to regional variability related largely to the passage of storms and forced uplift of air masses by orography (orographic precipitation). Convective precipitation (thunderstorms), caused by strong surface heating, is found over land areas in summer. However, convective precipitation also occurs over the ice-free ocean in some circumstances.

For the Arctic as a whole, annual precipitation for the October 2024-September 2025 water year was the highest on record. This has reinforced upward trends in precipitation as observed over the period 1950-2025. The year 2025 also saw the widespread occurrence of extreme precipitation events in winter, as well as summer dryness. As the water cycle intensifies and extreme precipitation events become more common (Yu and Zhong 2021; Dou et al. 2022), disruption to ecosystems (e.g., Christensen et al. 2021; Serreze et al. 2021) and human infrastructure (e.g., Hansen et al. 2014; Fox et al. 2023) will further impact Arctic communities.

As with other essays in Arctic Report Card 2025, water-year seasons are defined as autumn (October-December), winter (January-March), spring (April-June), and summer (July- September). Anomalies are relative to the 1991-2020 average. The results presented here use both precipitation gauges and atmospheric reanalysis data, which are derived by assimilating observations with output from numerical weather prediction models. Atmospheric reanalysis data are helpful for filling in the many gaps in the sparse precipitation gauge network in the Arctic, especially over the Arctic Ocean, though in general in situ precipitation measurements are not assimilated.

Precipitation at a glance

The 2024/25 water year included several prominent features. Record-high precipitation for spring, and high ranks for autumn (4th highest) and winter (4th highest) stand in contrast to an unusually dry summer (35th highest). However, despite summer dryness, the water year, as a whole, ranked as the wettest on record. Regionally, below-average precipitation in autumn over the Barents Sea contrasted above-average precipitation over northern Europe, pointing to an eastward shift in storm tracks relative to average conditions. The Alaskan Panhandle shifted from having above-average precipitation in autumn to below-average precipitation in winter. This reflects a westward location of low pressure from over the Gulf of Alaska in autumn to over the Aleutian Islands in winter (see Fig. 3 in essay Surface Air Temperature). The summer dryness was especially apparent over large parts of Eurasia and northern Canada, likely contributing to the frequent Canadian forest fires. Figure 1 shows seasonal precipitation totals derived from ERA5 reanalysis during the 2024/25 water year expressed as departures from the 1991-2020 means.

Heavy precipitation events

For any given year, regionally heavy precipitation events can approach or exceed previous records, even in a stable climate. Following the approach of previous Arctic Report Cards, Fig. 2 shows heavy precipitation events during the 2024/25 water year in terms of ranks of the maximum 5-day precipitation events (Rx5) in each season (relative to the 1950-2023 period). The standout feature is the comparatively higher density of heavy precipitation events across the Arctic in winter compared with the other seasons. One feature of special note is the band of heavy precipitation events in winter stretching northward from south of the Aleutian Islands across Alaska. Much of that precipitation was related to a large northward pulse of moisture (an “atmospheric river”) from 22-25 January. The associated southerly winds also contributed to warmer-than-average surface air temperatures across these areas (see essay Surface Air Temperature). Note also the band of heavy precipitation in summer over northern Alaska.

Historical perspective

The last several Arctic Report Cards have highlighted that, as assessed over the available period of record, there are upward trends in pan-Arctic precipitation in the annual mean average and for each season individually. Previous studies commenting on trends (Box et al. 2021; Yeh et al. 2021; Yu and Zhong 2021; Walsh et al. 2022) emphasize interannual and multiyear variability and large regional variations. There is also evidence of a transition from solid to liquid precipitation in the warmer parts of the Arctic (Box et al. 2021).

Following previous Arctic Report Cards, the Arctic precipitation time series from ERA5 (as a percentage of 1991-2020 averages for the region poleward of 60° N) is plotted along with the corresponding time series from the station-based dataset of the Global Precipitation Climatology Center (GPCC) during 1950/51-2024/25 (Fig. 3). The ERA5 data cover ocean areas as well as land, while the GPCC dataset is for land only. While the percent anomaly time series are generally similar, there are some substantial differences for individual years due to the absence of coverage over the Arctic Ocean in GPCC and inherent uncertainties in each data source.

The record-high rank of annual mean precipitation for the 2024/25 water year, as well as the high ranks for individual seasons (a record-high for spring), served to reinforce the conclusion that precipitation for the Arctic region overall is increasing. Based on the ERA5 precipitation time series for the region poleward of 60° N that includes the 2024/25 water year, the trend in annual mean precipitation stands at 0.75 cm per decade. Corresponding seasonal trends are 0.22 cm per decade for autumn, 0.23 cm per decade for winter, 0.13 cm per year for spring, and 0.09 cm per decade for summer. Autumn and winter hence show the strongest seasonal trends. In terms of percent change relative to the 1991-2020 average, winter is strongest (2.25 % per decade). Autumn is 1.67 % per decade, summer is 1.04% per decade, spring is 1.11% per decade, and the water year as a whole is 1.47% per decade.

The spatial pattern of annual trends, 1950-2025, is quite revealing (Fig. 4). Positive trends of up to 0.3 cm per year are apparent over the North Atlantic sector of the Arctic and extending into the Barents Sea. The strong positive trends along the Norwegian coast and parts of the southeast coast of Greenland point to orographic effects—forced uplift and cooling of moist air. Strong positive trends along the Alaska coast are also consistent with orographic uplift. Pointing further to the spatial heterogeneity of trends, reductions in precipitation are seen in other areas, such as parts of northern Eurasia and Canada.

Methods and data

Because of the challenges of collecting in situ precipitation gauge measurements in the Arctic, we use gridded precipitation fields from both the ERA5 atmospheric reanalysis of the European Centre for Medium Range Weather Forecasts (ECMWF) (Hersbach at al. 2020) and the Global Precipitation Climatology Centre’s GPCC Full Data Version Data Version 2022 (Becker et al. 2013; https://opendata.dwd.de/climate_environment/GPCC/html/fulldata-daily_v2022_doi_download.html). ERA5 data are available from January 1940 onward, but the quality of the output is more reliable starting in 1979 (Hersbach et al. 2020), after which modern satellite data are assimilated into the analysis and forecast system. ERA5 is the latest atmospheric reanalysis effort and performs slightly better than other atmospheric reanalyses at matching observed precipitation totals from Arctic extreme events (Loeb et al. 2022). Given the model-derived nature of ERA5, comparisons are made with the GPCC’s full data product, a monthly gridded gauge-based product available from 1891 onward (Schneider et al. 2022). Our comparisons of pan-Arctic precipitation computed from these two sources is limited to the post-1950 period because both products were impacted by missing data during World War II.

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November 21, 2025