Drought in Delaware

Note:  The next drought report will be on September 3rd, 2025

Highlights:

• Precipitation has been well above normal for the past month in most locations. Even with high evapotranspiration rates, most locations still rain a water balance surplus for the month of July.
• Soil moisture conditions are seasonable for this time of year
• Streamflow and groundwater conditions are around the median (e.g., average) level for this time of year at most locations around the state
• Warm and wet conditions are expected to persist through the remainder of the summer and into early fall

Statewide Drought Discussion

Delaware is currently not experiencing any drought conditions. 

Precipitation

Wet conditions have persisted throughout the month of July statewide.  Monthly totals ranged from 4 to 5 inches in Newark, Milford, and Port Penn to 10+ inches in Claymont, Woodside, and Hockessin (Figure 1).  While precipitation varied significantly throughout the state, every location received above normal precipitation relative to the 1991-2020 normals period.

Looking beyond the last month, precipitation in Delaware has been between 125 and 150% of normal over the last two to three months, with the bulk of that coming in July.  Barring a very dry August, the summer of 2025 precipitation should end up well above normal for the Delaware.   

Temperature/Evapotranspiration

Normally, Delaware would be in deficit in the water balance this time of year, as evapotranspiration normally outpaces precipitation in July and August.  However, precipitation has exceeded the loss of water from the environment over the past month or so, including some areas with 4 to 5 inch surpluses over that time period (e.g., Greater Wilmington Area).  While temperatures were normal to above normal throughout most of July, recent temperatures have been much lower, thus lowering the evapotranspiration rate across the state.  

Soil Moisture

Figure 2 shows soil moisture conditions through the state and most of the region are normal for this time of year.  Portions of Kent County are even experiencing above normal soil moisture in the top meter of soil right now.  Most non-irrigated agricultural fields are at or near peak evapotranspiration right now.  But with the recent wet conditions, even those fields have sufficient soil moisture for optimal growth and the same is likely true for lawns and gardens. 

Streamflow

 The daily average flows for all of the major streams in northern New Castle County have been hovering at or just above their respective medians for the past several weeks.  It’s been since September 2024 since the 30-day average flows on both the White Clay Creek at Newark and on the White Clay Creek near Newark have been this high. In addition, it’s been since May 2024 since flows have been this high on the Brandywine. Above normal precipitation during the months of June and July have helped maintain higher flows when they tend to decrease rapidly during days of high evapotranspiration. Thirty-day average flows on streams in Kent and Sussex Counties have also been hovering around their respective medians for the past couple of weeks.

Chlorides

Chloride concentrations in the Christina River near Newport remain well below the first threshold of concern (250 ppm) at 3.08 ppm, and the salt front on the Delaware River has been below the 250 ppm threshold since at least mid-February.

Chloride concentrations have been very low since March 5th, when they reached 263.2 ppm.

Groundwater

Groundwater conditions in the unconfined aquifer (i.e., surficial aquifer) in northern New Castle County remained steady over the past several weeks.  DGS well Db24-18 (located just south of Newark) remained steady at a depth of approximately 12.4 ft below land surface (Table 1).  The water level in this well typically ranges between 11.0 and 13.4 feet below land surface during August.   Elsewhere, groundwater levels around the state remain a mixed bag. Hb12-05, located in New Castle County, is at its “average” depth for August, Mc51-01a, located in southwestern Kent County is struggling to rise above “below normal.”  Pf24-02, located in Sussex County (Figure 3), is at the “above normal” range.

Weather and Climate Outlook

Very little precipitation is expected over the next week to 10 days.  Given that nearly all drought indicators are in good shape right now, drought development is unlikely in the short term.  Drought formation in Delaware in late summer/early fall is also looking fairly unlikely at this time.  Warm, wet conditions are expected to persist throughout our region over that time period according to NOAA’s Climate Prediction Center (Figures 4 and 5).  Overall, this has been the trend throughout the summer for our part of the country, and with the larger scale weather patterns we’ve been experiencing expected to remain in place, we should expect Delaware to remain drought free for the most part over that time frame.

One last item that’s worth mentioning is that we have arrived at the time of year when hurricane activity starts to pick up in the Atlantic basin.  August and September tend to be the months when tropical systems affect Delaware most often.  Thus, we’ll need to keep our eye on the tropics, as rain from tropical systems can often be an effective way to end mild-to-moderate drought, should one form over the next couple of months.