September 2, 2025 National Drought Summary

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilizedinclude the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast webpage used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

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For the drought week of August 27th-September 2nd, 2025, relatively dry conditions were observed across the U.S. Virgin Islands (USVI) making this the second consecutive dry week since the passage of Hurricane Erin’s outer rain bands and locally heavy rainfall. This week was characterized by a mix of sunshine and periods of cloud cover, with generally scattered showers and a few thunderstorms. There were periods of elevated heat risk, especially late in the drought week with southeasterly flow bringing an increase in low-level moisture. Despite the approach of a mid-level trough from the northwest and moisture from a tropical wave passing south of the Islands, satellite-based (SPoRT IMERG) rainfall estimates over the last 7 days show that most of the precipitation remained southwest of the region.

On the island of St. Croix, weekly precipitation amounts ranged from 0.05-inch at VI-SC-29 (Frederiksted 2.5 NNE) to 1.04 inches at VI-SC-35 (Frederiksted 1.3 ENE). Intermediate precipitation values included 0.17-inch at VI-SC-24 (Christiansted 2.1 ENE, 3 days missing), 0.27-inch at VI-SC-23 (Christiansted 6.5 W), 0.30-inch at VI-SC-25 (Christiansted 4.4 W), 0.35-inch at VI-SC-34 (Frederiksted 1.9 NE), 0.39-inch at VI-SC-10 (Christiansted 1.6 E), an even half-inch at VI-SC-20 (Frederiksted 1.7 ESE), and 0.54-inch of rain at VI-SC-30 (Christiansted 1.7 SW). The Adventure 28 Well maximum and minimum water levels below the land surface ranged from 18.06 feet (2:45 a.m., August 28th) to 18.50 feet (4:45 p.m., September 2nd). Though there were relatively small rises and falls in water level throughout the drought week, an overall decline was noted. The Standardized Precipitation Index (SPI) values at the 1-, 3-, 6-, 9-, and 12-month periods for East Hill (#672560) were, respectively: -1.13, -1.64, -0.31, -0.23, and +0.71. Values have worsened (decreased) for each of the time periods compared to last week, except for the 12-month SPI which stayed the same. Given the weekly observed rainfall amounts, groundwater levels, and SPI values, St. Croix’s drought designation remains D1(S). The possibility of future degradation within the next few weeks will be monitored closely.

On St. John, weekly accumulated precipitation amounts ranged from 0.03-inch at VI-SJ-10 (Cruz Bay 3.1 NNW) to 0.90-inch at VI-SJ-8 (Cruz Bay 7.4 E). An intermediate total of 0.19-inch of rain was measured at Windswept Beach (VI-SJ-3). However, the observer noted 0.45-inch of rain fell shortly after this week’s data cutoff, and therefore will be included in next week’s precipitation total. The rainfall totals for the past three months are 7.26 inches in August, 2.07 inches in July, and 1.36 inches in June. The Susannaberg Dpw 3 Well maximum and minimum water levels below the land surface ranged from 12.43 feet (3:00 p.m., August 27th) to 12.67 feet (11:00 a.m., September 2nd). A slow decline in wellwater level was noted this week. The SPI values at the 1-, 3-, 6-, 9-, and 12-month periods for Windswept Beach were, respectively: +0.74, +0.19, +0.49, +0.51, and +0.68. Positive values at all the time ranges do not support any drought, despite the relatively light precipitation received this past drought week.

On the island of St. Thomas, weekly rainfall measurements included 0.16-inch at VI-ST-13 (Charlotte Amalie 1.2 NNW) and 0.17-inch at VI-ST-15 (Charlotte Amalie West 1.3 N). The Grade School 3 Well maximum and minimum water levels below the land surface ranged from 6.95 feet (3:00 p.m., August 27th) to 7.45 feet (9:00 a.m., September 2nd). A smooth decline in water level was noted during the week, except for a slight rise in water level towards the end of the period. The SPI values at the 1-, 3-, 6-, 9-, and 12-month periods for the Cyril E. King Airport (#11640) were, respectively: +0.04, -0.86, +0.41, +0.53, and +1.05, indicating similar numbers to last week. Though the weekly precipitation amounts were light and groundwater levels declined, drought-free conditions remain at St. Thomas.

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The U.S.-Affiliated Pacific Islands (USAPI) domain was primarily dominated by such features as trade wind troughs, weak circulations, the InterTropical Convergence Zone (ITCZ), the Monsoon Trough (MT), and regions of low-level convergent flow. South of the equator, the drought week was characterized by generally fair weather, subtropical ridging, and light precipitation on most days. Towards the end of the week, cloudiness and shower activity were increasing across the region, as an east-west-oriented ridge axis approached the region from the south, and a trough line approached from the north-northeast. Increasingly moderate-to-fresh southeast winds were occurring over the region as the ridge axis approached from the south. No major tropical cyclones were noted during this past drought week over the USAPI domain. Perhaps the most active weather occurred over the western Federated States of Micronesia (FSM) area and the nearby Republic of Palau. A monsoon pattern dominated this region during most of the past week. As the monsoon pattern evolved and drifted northward (accompanied by a surge in the monsoon flow), west-southwest winds set up over Palau and Yap, accompanied by very moist flow and periods of gusty showers and locally heavy rain. These west-southwest winds, which flow contrary to the usual easterly trade winds at these low latitudes are consistent with the location of the so-called “Monsoon Trough” (MT). Towards the end of the drought week, a subtropical ridge had settled across Palau and Yap, allowing winds and showers to briefly diminish.

Over the tropical western North Pacific, from about the equator to 10N and 130E to 170E (which encapsulates most of the USAPI region), quantitative precipitation estimates (QPE) from SPoRT IMERG satellite imagery ranged from about 0.5-4.0 inches. From about 10-15N along the same longitude band (which includes most of the Commonwealth of the Northern Mariana Islands (CNMI), only 0.5-1.0 inch amounts were generally noted. The satellite estimated rainfall for the CNMI region appears underdone in comparison to the rain gauge measurements described below. This may be due to a combination of factors such as the highly localized and rapidly changing convective conditions over this area, the limitations of satellite sensors in “seeing” through the tops of extremely deep convective clouds, and infrared satellite sensor inaccuracies when estimating rainfall rates based on cloud-top temperature which varies widely over the oceanic tropics. Local orographic enhancement may also be a partial contributor. Over American Samoa south of the equator, 0.5-inch or less of precipitation was estimated.

Across American Samoa, three-quarters of an inch of rain was measured at the Pago Pago WSO Airport, well shy of the 2-inch minimum requirement to meet most water needs for a week. The preliminary rainfall accumulation for the month of August is 3.45 inches (about half of its normal 6.93 inches), though 7 of the past 11 months have registered as “wet” (i.e., 8 inches or more). For the higher elevation sites of Siufaga Ridge and Toa Ridge, the past weekly and preliminary August monthly rainfall totals are, respectively: 0.49, 1.43 and 0.12, 1.15, which fall well short of minimum water requirements for a week and month. Despite the recent dryness, Tutuila maintains its dryness- and drought-free designation.

For the Commonwealth of the Northern Mariana Islands (CNMI), the Rota Airport measured 2.95 inches of precipitation for the past week and 14.79 inches for the August total (preliminary), both of which registered “wet” (i.e. met or exceeded the weekly and monthly precipitation thresholds of 1-inch and 4-inches, respectively). This marks the 8th consecutive wet week for Rota, as well as the third consecutive wet month. Rota continues to be drought-free. The Saipan International Airport reported 3.59 inches of rain this past drought week and 8.61 inches for August (preliminary), easily surpassing weekly and monthly water requirements. This marks the third consecutive wet month for the site. Accordingly, Saipan retains its drought-free status this week. In Agat, 2.38 and 11.58 inches of precipitation were noted for the past week and August (preliminary), respectively. Eleven of the past 12 weeks have been “wet”, as have the last 3 months. Dededo measured 2.04 inches of precipitation this week, marking the 8th consecutive wet week. Their August preliminary rainfall total is 9.35 inches. Tinian measured 1.49 inches of rain this past drought week, with 4.88 inches reported for the month of August (preliminary). Tinian was also “wet” in July, and remains drought-free. The island territory of Guam recorded 3.91 inches of rain this week, which is nearly as much as the monthly rainfall requirement (4 inches). This is now the tenth consecutive wet week. Guam received 13.06 inches of rain (provisional) in August, and the last three months were wet. The island territory remains drought-free this week.

The majority of stations across the Federated States of Micronesia (FSM) came in with adequate rainfall amounts this week to meet most water needs. Precipitation during the past week and for the month of August (provisional) at the FSM stations include, respectively: Pohnpei (6.59 inches, 22.54 inches), North Fanif (5.19, 14.15), Lukunoch (5.01, 12.20), Kosrae (4.56, 26.17), Chuuk (4.34, 13.74), Rumung (4.05, 15.69), Yap Island Airport (3.56, 10.23), Woleai (3.41, 10.65), Pingelap (2.52, 11.68), Kapingamarangi (1.79, 10.11), and Nukuoro (1.48, 7.55). Most of these reporting stations this week were “wet”, except for Kapingamarangi and Nukuoro which were “dry”. A few other statistics include: 11 of the past 12 weeks were wet, as were the past 11 months at Pohnpei; 4 consecutive wet months at North Fanif; 9 consecutive wet months at Lukunoch; 12 consecutive wet weeks and 11 consecutive wet months at Kosrae, 8 of the past 11 months were wet at Chuuk; 9 of the past 11 months were wet at the Woleai atoll; July and August 2025 were both wet months at Kapingamarangi; and 9 of the past 11 months were wet at Nukuoro. Dryness- and drought-free conditions continue this week at all these locations, including Nukuoro despite the marginal dryness this past week and month. No analysis was possible this week at Ulithi and Fananu due to lack of rainfall data.

The Republic of Palau experienced another very wet week and month. Koror measured 5.75 inches of rain this past week, making 11 of the past 12 weeks wet. The preliminary August total is 19.33, making the last 11 months wet. For Airai (WSO Palau), the weekly rainfall accumulation totaled 6.48 inches, and the preliminary August total is 18.91 inches. Drought-free conditions persist in Palau.

In the Republic of the Marshall Islands (RMI), Automatic Weather Stations (AWS) were installed in the atolls to gather precipitation data. The greatest precipitation total this week occurred at Ailinglaplap, where 6.10 inches of rain was reported, marking the 5th straight wet week. Ailinglaplap’s drought designation remains as drought-free. The next highest weekly rainfall amount was 4.83 inches at Kwajalein, with a provisional August total of 8.29 inches. The most recent week and month both registered as “wet” periods in Kwajalein. The last wet month reported at this site was in November of last year (2024) when 8.83 inches of rain fell. Despite these statistics, Kwajalein’s designation remains at D0-S (short-term dryness). Mili measured 3.90 inches of rain this week, with a preliminary August rainfall total of 12.09 inches. Mili remains drought-free this week. Majuro came in with 1.68 inches of rain this week which registers as “dry”, though 9 of the past 12 weeks were wet. The provisional August total is 10.76 inches, and the last 3 months have been wet. Despite this most recent dry week, Majuro retains its drought-free depiction. Finally, 0.63-inch of precipitation fell at Utirik this week, with a preliminary August total of 4.29 inches. Utirik’s drought designation remains as short-term moderate drought (D1-S). Due to the unavailability of rainfall data at Jaluit and Wotje, no analysis was performed at those stations.

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