Overview Realtime Historical Map View
Heat Advisory
2026-07-15T20:00:00-04:00

* WHAT...Heat index values up to 105 expected. * WHERE...Portions of DC, central, north central, northeast, northern, and southern Maryland, and central, northern, and northwest Virginia. * WHEN...From 11 AM to 8 PM EDT Wednesday. * IMPACTS...Hot temperatures and high humidity may cause heat illnesses.

Difficult Run Near Great Falls, Va Historical Data

Historical Data


Streamflow Range


Date Average 2026 2025 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011
01-01 67.09
01-02 133.96
01-03 44.47
01-04 59.12
01-05 60.89
01-06 42.37
01-07 76.57
01-08 45.18
01-09 39.67
01-10 283.97
01-11 80.91
01-12 81.77
01-13 121.33
01-14 55.95
01-15 51.82
01-16 46.8
01-17 88.81
01-18 52.97
01-19 48.19
01-20 146.94
01-21 53.57
01-22 41.33
01-23 38.72
01-24 50.01
01-25 92.29
01-26 80.19
01-27 49.89
01-28 63.92
01-29 69.15
01-30 46.04
01-31 399.16
02-01 75.65
02-02 89.0
02-03 55.11
02-04 111.14
02-05 107.7
02-06 60.22
02-07 63.26
02-08 64.47
02-09 46.01
02-10 45.96
02-11 69.37
02-12 72.05
02-13 106.07
02-14 77.77
02-15 57.43
02-16 182.05
02-17 102.09
02-18 68.96
02-19 57.78
02-20 91.98
02-21 72.89
02-22 78.25
02-23 78.49
02-24 72.64
02-25 166.76
02-26 57.1
02-27 83.79
02-28 51.54
02-29 52.7
03-01 96.39
03-02 111.15
03-03 70.39
03-04 117.04
03-05 68.03
03-06 70.81
03-07 81.61
03-08 61.47
03-09 69.85
03-10 113.88
03-11 97.91
03-12 59.12
03-13 73.31
03-14 51.02
03-15 57.19
03-16 45.06
03-17 115.51
03-18 48.96
03-19 56.6
03-20 57.53
03-21 61.85
03-22 181.66
03-23 56.71
03-24 56.8
03-25 93.49
03-26 63.06
03-27 47.15
03-28 55.75
03-29 67.64
03-30 94.78
03-31 143.21
04-01 107.73
04-02 56.67
04-03 55.13
04-04 58.11
04-05 44.17
04-06 73.03
04-07 67.61
04-08 91.02
04-09 46.97
04-10 46.67
04-11 40.46
04-12 62.7
04-13 49.06
04-14 57.3
04-15 70.33
04-16 106.27
04-17 55.42
04-18 43.55
04-19 53.6
04-20 96.87
04-21 67.34
04-22 40.7
04-23 77.26
04-24 55.36
04-25 45.44
04-26 57.94
04-27 48.27
04-28 45.48
04-29 67.22
04-30 69.08
05-01 324.48
05-02 64.1
05-03 173.36
05-04 107.22
05-05 90.31
05-06 100.72
05-07 195.03
05-08 83.71
05-09 50.0
05-10 45.75
05-11 64.36
05-12 85.15
05-13 55.52
05-14 173.56
05-15 174.62
05-16 127.82
05-17 98.2
05-18 66.41
05-19 77.41
05-20 58.08
05-21 52.3
05-22 56.95
05-23 147.87
05-24 117.13
05-25 58.43
05-26 44.52
05-27 79.66
05-28 81.77
05-29 119.03
05-30 91.53
05-31 51.26
06-01 140.69
06-02 127.37
06-03 69.64
06-04 127.56
06-05 85.33
06-06 58.59
06-07 31.84
06-08 51.78
06-09 114.73
06-10 36.22
06-11 160.64
06-12 151.1
06-13 63.19
06-14 185.46
06-15 131.79
06-16 61.92
06-17 96.68
06-18 45.87
06-19 73.81
06-20 91.02
06-21 142.23
06-22 39.76
06-23 124.73
06-24 76.4
06-25 31.78
06-26 32.72
06-27 22.29
06-28 75.77
06-29 69.75
06-30 26.71
07-01 27.15
07-02 135.83
07-03 47.02
07-04 94.44
07-05 49.97
07-06 33.62
07-07 49.84
07-08 29.28
07-09 381.74
07-10 72.37
07-11 112.78
07-12 43.11
07-13 196.36
07-14 126.61
07-15 84.69
07-16 117.29
07-17 44.98
07-18 43.45
07-19 33.69
07-20 38.06
07-21 25.52
07-22 469.53
07-23 105.24
07-24 115.03
07-25 49.89
07-26 84.42
07-27 23.94
07-28 37.44
07-29 197.7
07-30 38.98
07-31 98.26
08-01 45.76
08-02 91.56
08-03 31.23
08-04 44.45
08-05 53.04
08-06 45.44
08-07 114.36
08-08 176.03
08-09 31.79
08-10 21.51
08-11 133.7
08-12 25.99
08-13 151.88
08-14 76.26
08-15 27.56
08-16 53.22
08-17 42.2
08-18 36.63
08-19 79.9
08-20 126.21
08-21 65.25
08-22 178.05
08-23 41.91
08-24 40.04
08-25 20.7
08-26 33.24
08-27 24.58
08-28 53.1
08-29 70.67
08-30 27.67
08-31 18.51
09-01 47.4
09-02 95.96
09-03 34.72
09-04 23.42
09-05 17.75
09-06 21.84
09-07 83.13
09-08 94.33
09-09 649.25
09-10 166.69
09-11 34.9
09-12 27.67
09-13 87.99
09-14 21.86
09-15 17.88
09-16 16.81
09-17 49.62
09-18 28.83
09-19 32.06
09-20 19.82
09-21 17.28
09-22 18.44
09-23 19.45
09-24 71.91
09-25 41.54
09-26 30.47
09-27 21.97
09-28 90.59
09-29 35.23
09-30 136.46
10-01 25.37
10-02 33.36
10-03 64.59
10-04 30.51
10-05 21.09
10-06 19.29
10-07 17.63
10-08 27.65
10-09 19.94
10-10 24.17
10-11 38.03
10-12 284.44
10-13 40.16
10-14 172.19
10-15 41.93
10-16 43.28
10-17 34.63
10-18 21.4
10-19 18.62
10-20 29.03
10-21 40.12
10-22 23.72
10-23 31.93
10-24 20.24
10-25 19.99
10-26 154.78
10-27 43.88
10-28 34.94
10-29 53.36
10-30 305.69
10-31 62.72
11-01 151.46
11-02 36.53
11-03 122.51
11-04 28.55
11-05 28.11
11-06 40.21
11-07 40.73
11-08 62.92
11-09 29.63
11-10 45.13
11-11 32.54
11-12 121.62
11-13 62.95
11-14 39.7
11-15 29.93
11-16 190.02
11-17 45.59
11-18 41.52
11-19 30.91
11-20 28.71
11-21 25.44
11-22 133.09
11-23 48.23
11-24 36.89
11-25 166.11
11-26 32.82
11-27 101.04
11-28 43.16
11-29 31.13
11-30 39.23
12-01 61.75
12-02 46.54
12-03 50.42
12-04 36.51
12-05 33.65
12-06 34.62
12-07 101.42
12-08 162.91
12-09 41.63
12-10 70.06
12-11 108.96
12-12 40.66
12-13 32.66
12-14 32.95
12-15 60.4
12-16 302.5
12-17 172.48
12-18 261.75
12-19 49.31
12-20 39.12
12-21 51.64
12-22 63.71
12-23 216.44
12-24 85.88
12-25 198.19
12-26 82.21
12-27 152.82
12-28 100.01
12-29 65.07
12-30 89.1
12-31 50.77

Annual Peak Streamflow


Seasonal Comparison


Oceanic Nino Index