The mountains of the western United States are sporting thin winter coats in early 2026. Although most regions saw average or above-average precipitation in fall and early winter, warmer temperatures meant that much of it fell as rain. The result has been an unusually low snowpack for this time of year, constituting a snow drought .
2026 年初，美国西部山区披上了薄薄的冬衣。尽管大多数地区秋季和初冬的降水量处于平均或高于平均水平，但气温升高意味着大部分降水以降雨形式出现。结果是一年中这个时候积雪异常低，构成雪旱。
This image, acquired with the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite, provides a wide view of meager western snow cover on January 15. On that day, measurements derived from satellite observations showed that snow blanketed 142,700 square miles (369,700 square kilometers) of the west. That’s the lowest coverage for that date in the MODIS record dating back to 2001 and less than one-third of the median. Coverage had increased slightly by January 26.
这张图像是用美国宇航局 Terra 卫星上的 MODIS（中分辨率成像光谱仪）拍摄的，提供了 1 月 15 日西部薄薄的积雪的广阔视野。当天，卫星观测的测量结果显示，积雪覆盖了西部 142,700 平方英里（369,700 平方公里）的面积。这是自 2001 年以来 MODIS 记录中该日期的最低覆盖率，不到中位数的三分之一。截至 1 月 26 日，覆盖范围略有增加。
In addition to snow cover area, snow water equivalent (SWE)—the amount of water stored in the snowpack—is an important indicator of winter conditions in the West. In early January, the National Integrated Drought Information System reported that snow drought, defined as SWE below the 20th percentile for a given date, was most acute in Washington, Oregon, Colorado, Utah, Arizona, and New Mexico. At least one ground-based monitoring station in every major western watershed recorded the lowest SWE in at least 20 years on January 26, according to data published by the USDA Natural Resources Conservation Service .
除了积雪面积之外，雪水当量（SWE）——积雪中储存的水量——是西方冬季状况的重要指标。 1 月初，国家综合干旱信息系统报告称，雪旱（定义为特定日期的 SWE 低于 20%）在华盛顿、俄勒冈、科罗拉多、犹他、亚利桑那和新墨西哥州最为严重。根据美国农业部自然资源保护局公布的数据，1 月 26 日，西部每个主要流域至少有一个地面监测站记录了至少 20 年来的最低 SWE。
Overall, the preceding few months were very wet and warm across the West. For the water year beginning on October 1, 2025, many regions saw average or above-average precipitation . However, record warmth across a vast expanse of the region meant that much of that precipitation fell as rain rather than snow. A December 2025 atmospheric river in the Pacific Northwest was one such warm precipitation event.
总体而言，过去几个月西部地区非常潮湿和温暖。 2025年10月1日开始的水年，许多地区的降水量达到平均或高于平均水平。然而，该地区大片地区创纪录的温暖意味着大部分降水都是雨而不是雪。 2025 年 12 月太平洋西北地区的一条大气河流就是这样一个温暖的降水事件。
One nuance in the snow deficit picture can be found in the Southern Sierra and Northern Rockies, where more precipitation has fallen as snow than rain on the lofty peaks. SWE levels stood above average at some high-elevation locations but were low farther downslope. “This is a classic climate-change, temperature-driven, elevationally dependent snowpack deficit,” said Daniel Swain, climate scientist at the California Institute for Water Resources, in a presentation .
雪亏状况的一个细微差别可以在南山脉和北落基山脉发现，那里高耸的山峰上降雪量多于降雨量。在一些高海拔地区，SWE 水平高于平均水平，但在下坡处则较低。加州水资源研究所的气候科学家丹尼尔·斯温（Daniel Swain）在一次演讲中表示：“这是典型的气候变化、温度驱动、海拔相关的积雪不足。”
Precipitation falling as rain tends to run off before it can recharge reservoirs and groundwater. On the other hand, winter snowpack that melts in the spring can produce a more metered, sustained water supply. The health of the mountain snowpack has implications for ecosystems, wildfire dynamics, and water availability for agriculture and other uses during drier times of the year.
由于雨水在补充水库和地下水之前往往会流失，导致降水量下降。另一方面，冬季积雪在春季融化可以产生更加计量、持续的供水。山地积雪的健康状况对生态系统、野火动态以及一年中干旱时期农业和其他用途的可用水量都有影响。
There is still a lot of winter remaining, and February and March can bring significant amounts of snow. But snowfall in the coming months may not be able to make up for existing deficits. In places such as the Pacific Northwest and the Colorado River Basin that are already dry, snow drought may turn into or exacerbate traditional drought.
冬季还剩很长一段时间，二月和三月可能会带来大量降雪。但未来几个月的降雪可能无法弥补现有的赤字。在太平洋西北地区和科罗拉多河流域等已经干旱的地区，雪旱可能会转变为或加剧传统干旱。
NASA Earth Observatory image and chart by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview , and snow cover area data from NSIDC Snow Today . Story by Lindsey Doermann.
Michala Garrison 提供的 NASA 地球观测站图像和图表，使用来自 NASA EOSDIS LANCE 和 GIBS/Worldview 的 MODIS 数据，以及来自 NSIDC Snow Today 的积雪面积数据。林赛·杜尔曼的故事。