Waterlands
Difficult Run
USGS · 01645704
DIFFICULT RUN
USGS · 01645704LIVE

DIFFICULT RUN ABOVE FOX LAKE NEAR FAIRFAX, VA

RESTON, VA38.8847°N, -77.3324°W Updated 9 hr ago
FLOW RATE
22cfs
GAUGE HT
1.46ft
WATER TEMP
77°F
AIR TEMP
72°F
WIND
4mph NNE
FISH INDEX
69SCORE / 100
GREAT · 4 OF 5
Flow Rate Historical Avg
MEDIAN FLOW RATE · 7 DAY
22cfs 58.3% vs avg
Optimal band: 1216 cfs
PERIOD HIGH
55cfs
PERIOD LOW
1cfs
RUNNABLE
13%
last 7 day in band

Gauge Height

1.46ft

Water Temperature

77.4°F

Water Turbidity

Precipitation History

Precipitation · YTD

Normal

Near-normal year

2026 to date

22.3in

≈ normal

22.34 in of precipitation so far this year — about average for this point in the season (normal 22.5 in).

YTD Total

22.3in

This year so far

Normal to Date

22.5in

30-yr average

Typical Range

16.7–28.7in

10th–90th pct YTD

Departure

-1%

vs 30-yr normal

By Month

This year
Typical range
Normal
Jan: 3.02" · normal 3.13" (1.7–4.5)
Jan
Feb: 2.66" · normal 2.85" (1.5–4.4)
Feb
Mar: 3.34" · normal 3.90" (1.7–5.2)
Mar
Apr: 1.99" · normal 3.49" (1.7–5.0)
Apr
May: 4.03" · normal 3.94" (2.1–6.5)
May
Jun: 3.97" · normal 3.64" (1.7–6.0)
Jun
Jul: 3.34" (so far)· normal 4.23" (2.1–7.0)
Jul
Aug: normal 3.77" (1.9–5.1)
Aug
Sep: normal 4.73" (1.4–8.3)
Sep
Oct: normal 3.49" (1.2–5.1)
Oct
Nov: normal 3.04" (1.1–5.5)
Nov
Dec: normal 3.54" (2.0–5.4)
Dec
Baseline 19912020 · Source: Open-Meteo03:01 UTC
Your History · DIFFICULT RUN ABOVE FOX LAKE NEAR FAIRFAX, VA

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Weather Conditions
WEATHER CONDITIONS
TODAY
83°
71°
MON
84°
65°
TUE
90°
66°
WED
99°
69°
THU
98°
79°
FRI
92°
75°
SAT
92°
68°
TIME
SUN
9
NOW
10
am
11
am
12
pm
1
pm
2
pm
3
pm
4
pm
5
pm
6
pm
7
pm
8
pm
9
pm
10
pm
11
pm
MON
12
am
1
am
2
am
3
am
4
am
5
am
6
am
7
am
8
am
9
am
10
am
11
am
12
pm
1
pm
2
pm
3
pm
4
pm
5
pm
6
pm
7
pm
8
pm
9
pm
10
pm
11
pm
TUE
12
am
1
am
2
am
3
am
4
am
5
am
6
am
7
am
8
am
9
am
10
am
11
am
12
pm
1
pm
2
pm
3
pm
4
pm
5
pm
6
pm
7
pm
8
pm
9
pm
10
pm
11
pm
WED
12
am
1
am
2
am
3
am
4
am
5
am
6
am
7
am
8
am
9
am
10
am
11
am
12
pm
1
pm
2
pm
3
pm
4
pm
5
pm
6
pm
7
pm
8
pm
9
pm
10
pm
11
pm
THU
12
am
1
am
2
am
3
am
4
am
5
am
6
am
7
am
8
am
9
am
10
am
11
am
12
pm
1
pm
2
pm
3
pm
4
pm
5
pm
6
pm
7
pm
8
pm
9
pm
10
pm
11
pm
FRI
12
am
1
am
2
am
3
am
4
am
TEMP
hourly forecast
76°
mild
76°
76°
78°
80°
81°
82°
83°
83°
82°
81°
79°
76°
74°
72°
71°
70°
69°
68°
67°
66°
66°
65°
67°
71°
75°
77°
79°
80°
82°
83°
84°
84°
84°
84°
82°
79°
75°
73°
72°
71°
69°
68°
67°
67°
67°
66°
68°
71°
75°
79°
83°
85°
87°
89°
90°
90°
90°
89°
87°
82°
79°
76°
74°
73°
72°
71°
70°
70°
69°
70°
71°
75°
80°
85°
89°
91°
94°
97°
99°
99°
99°
99°
97°
91°
88°
87°
85°
84°
82°
82°
81°
80°
79°
79°
79°
82°
85°
88°
90°
93°
96°
98°
98°
95°
91°
92°
91°
87°
85°
82°
80°
79°
78°
77°
76°
76°
WIND
mph · gust · dir
7mph ENE
G 13 mph
7
G13
ENE
8
G14
ENE
8
G14
E
8
G13
E
8
G11
E
6
G9
E
6
G9
ESE
6
G9
SE
7
G11
SE
6
G11
SE
5
G12
SE
5
G16
SE
5
G17
ESE
5
G13
SE
5
G13
SE
4
G12
SSE
5
G12
SSE
4
G11
SSE
4
G9
S
2
G4
SW
4
N
3
NE
2
G3
E
2
G3
E
2
G6
ESE
3
G7
SE
3
G6
SE
3
G5
SSE
4
G5
SSE
5
G6
S
5
G7
S
4
G5
SSW
4
G6
SSW
3
G5
SSW
3
G6
S
5
G10
SSE
5
G11
S
6
G15
S
7
G17
S
7
G16
S
5
G13
S
4
G10
SSW
3
G8
SSW
3
G4
WNW
3
W
3
G4
WNW
3
N
1
G2
NW
0
G1
S
0
G1
N
2
SSE
3
SSW
4
SSW
4
SSW
3
SSW
4
SSW
4
G5
SSW
4
G5
SSW
4
G7
SSW
4
G7
SW
5
G9
SSW
5
G11
SSW
6
G17
SSW
6
G18
SSW
5
G16
SW
5
G13
SW
5
G11
SW
4
G6
WSW
4
G6
W
4
G6
W
4
G9
W
4
G11
W
4
G12
WNW
6
G13
WNW
6
G13
WNW
7
G11
NW
6
G9
WNW
6
G9
W
6
G9
WNW
6
G10
WNW
5
G11
WNW
4
G12
W
3
G12
WSW
2
G10
NW
3
NW
3
WNW
3
G5
W
4
G8
WNW
4
G11
WNW
5
G17
NW
5
G17
NW
5
G15
NW
6
G16
NW
5
G14
NW
4
G15
NW
7
G15
NW
8
G15
NW
9
G15
NW
10
G16
NW
10
G16
NW
9
G17
WNW
10
G17
WNW
10
G17
WNW
12
G17
NNW
9
G17
NNW
9
G19
NNW
7
G19
NNW
8
G21
NNW
8
G23
NNW
8
G24
NNW
8
G24
NNW
7
G21
NNW
6
G17
NNW
5
G13
NNW
4
G12
NNW
4
G12
NNW
PRECIP
chance %
4%
4%
6%
6%
7%
7%
9%
10%
13%
12%
7%
6%
1%
1%
1%
1%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
1%
1%
1%
1%
1%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
1%
1%
1%
1%
1%
1%
2%
2%
2%
2%
2%
2%
6%
6%
6%
6%
6%
6%
1%
1%
1%
1%
1%
1%
1%
1%
1%
1%
1%
1%
2%
2%
2%
2%
2%
2%
8%
8%
8%
8%
8%
8%
8%
8%
CLOUDS
cover %
100%
overcast
100%
100%
90%
100%
100%
100%
100%
100%
100%
100%
100%
100%
100%
92%
56%
24%
53%
100%
99%
100%
94%
100%
18%
0%
1%
3%
5%
0%
0%
0%
0%
3%
0%
0%
0%
0%
0%
0%
0%
25%
100%
75%
100%
100%
100%
100%
100%
100%
100%
26%
90%
6%
0%
0%
0%
5%
5%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
100%
100%
81%
100%
100%
100%
6%
1%
6%
12%
22%
84%
88%
100%
100%
13%
34%
73%
100%
100%
92%
82%
75%
68%
PRESSURE
hPa · trend
1009
1009100910091010101110101009100910101007100510041004100110001000100199910011003
TemperatureWind / GustsPrecipitationCloud coverPressure
Nowscroll →
FISH INDEX
69
Temperature
Warm
Wind
Calm
Pressure
Rising — Slow
Moon Phase
Average
DAYLIGHT
SUNRISE
05:54 AM
SUNSET
08:35 PM
14H 41M OF DAYLIGHT
MOON PHASE
Waning Crescent
6% illuminated

Station Location

38.8847, -77.3324
Loading map…
DATA · USGS · NOAA · NWSUPDATED 2026-07-12 00:00 UTC
Site #01645704·USGS

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