Drought in Delaware

Note:  The next drought report will be on July 23rd, 2025

Highlights:

• Precipitation varied quite a bit over the past week, with southern Delaware receiving about 200% of normal for the past 7 days, while northern Delaware received about 50% of normal for the same time frame.
• 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 throughout the remainder of the July.

Statewide Drought Discussion

Drought conditions for the state have remained fairly stable over the last two weeks.

Precipitation 

June 2025 ended up a dry month for Delaware, with the statewide average coming in about 1.5 inches below normal.  However, July has started off much better for most of the state.  Delaware experienced several days with showers and thunderstorms since the calendar rolled over to July.  Rainfall totals range from 1.5 to 2.5 inches across most of Kent and Sussex counties (see Figure 1).  Meanwhile, New Castle County received slightly less precipitation, with most locations there seeing 0.75 to 1.0 inches of rain in the past week or so.  These month-to-date rainfall totals are about 200% of normal south of Dover and about half of normal north of Dover. 

Temperature/Evapotranspiration

Temperatures have been slightly above normal over the last week, however evapotranspiration has been typical for this time of year due to the humid conditions we’ve been experiencing.  High humidity limits the rate of evapotranspiration.  The statewide average reference evapotranspiration since July 1st is 1.51 inches according to data from the DEOS Network.  With most locations receiving at least this much precipitation, the surface water balance is near zero to slightly positive for most of Delaware, with southern New Castle County being the only part of the state definitively in a deficit so far in July. 

Soil Moisture

With mostly adequate precipitation falling in recent days, soil moisture conditions in the upper meter of soil is well within the normal range statewide for this time of year, with a few locations even slightly above normal (Figure 2).  That doesn’t mean soil conditions are necessarily “wet”, but they are seasonable for this time of year, which is important for drought considerations.

Streamflow

The daily average flows for all of the major streams in northern New Castle County have been hovering around their respective medians for the past several weeks.  Summertime storms have helped maintain higher flows when they tend to decrease rapidly during days of high evapotranspiration. With the exception of the Nanticoke River, daily average flows on streams in Kent and Sussex Counties have also been hovering around their respective medians for the past month.  Flows on the Nanticoke River near Bridgeville have been very low since at least last August.

Chlorides

Chloride concentrations in the Christina River near Newport remain well below the first threshold of concern (250 ppm) at 1.96 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 at approximately 12.4 ft below land surface for the past 3 weeks (Table 1), which is about 0.3 feet above the below normal level for this time of year. The water level in this well typically ranges between 10.1 and 12.7 feet below land surface during July.   Elsewhere, groundwater levels around the state remain a mixed bag.  Figure 3 shows the groundwater levels at USGS well Pf24-02, which is located in central Sussex County.  Groundwater conditions there have been fairly stable since May as a result of the wet spring experienced in that part of the state.  

Weather and Climate Outlook

The precipitation outlook remains fairly wet over the next week, as a couple of weak frontal boundaries lead to more unsettled weather for our region.  Temperatures will also remain slightly above normal, which means slightly higher evapotranspiration rates as well.   With relatively wet conditions expected, we shouldn’t expect to see much change in soil moisture conditions.

For the remainder of July, NOAA’s Climate Prediction Center is predicting a continuation of the recent weather pattern we’ve been in:  warm and wet.  Assuming the long-range forecast verifies, we should expect drought conditions to remain stable over the next few weeks with no significant deterioration.