Record envelope, standing records and threshold days for Great Falls (USC00183850), Maryland, United States, with 58 years of record.
Key Facts for Great Falls
Great Falls (USC00183850) is a weather station in Maryland, United States at 39.00 latitude and -77.25 longitude, 61 m (200 ft) above sea level.
The station reports from 1893 to 1950, 58 years of record.
1,464 records set at Great Falls still stand.
Records are tracked for tmax, tmin, prcp: an element needs 30 years of data to be eligible.
Great Falls set a daily record low maximum temperature of 15.0 C (59.0 F) on 25 September 1950.
About the Station
Location: Maryland, United States, 39.00 latitude, -77.25 longitude.
Elevation: 61 m (200 ft).
Period of record: 1893 to 1950, 58 years.
Eligible elements: tmax, tmin, prcp.
Daily Record Envelope and 2026
0 days at or beyond a record
Record highRecord low2026 daily maximum2026 daily minimum
The band shows the record high and record low for each calendar day at Great Falls. The lines show the 2026 daily maximum and minimum. 0 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.
Daily record high and record low at Great Falls, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
26.7 C (80.1 F)
-29.4 C (-20.9 F)
n/a
n/a
Feb
27.8 C (82.0 F)
-25.6 C (-14.1 F)
n/a
n/a
Mar
32.8 C (91.0 F)
-15.0 C (5.0 F)
n/a
n/a
Apr
36.1 C (97.0 F)
-10.0 C (14.0 F)
n/a
n/a
May
37.2 C (99.0 F)
-2.2 C (28.0 F)
n/a
n/a
Jun
39.4 C (102.9 F)
3.3 C (37.9 F)
n/a
n/a
Jul
41.1 C (106.0 F)
7.2 C (45.0 F)
n/a
n/a
Aug
40.6 C (105.1 F)
3.3 C (37.9 F)
n/a
n/a
Sep
38.3 C (100.9 F)
0.6 C (33.1 F)
n/a
n/a
Oct
36.7 C (98.1 F)
-6.1 C (21.0 F)
n/a
n/a
Nov
27.8 C (82.0 F)
-16.7 C (1.9 F)
n/a
n/a
Dec
23.9 C (75.0 F)
-24.4 C (-11.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Great Falls still stand. 1930 holds the most, with 71.
Standing records at Great Falls by the year they were set
Year set
Standing records
1897
5
1898
24
1899
26
1900
49
1901
41
1902
27
1903
29
1904
31
1905
27
1906
25
1907
27
1908
25
1909
27
1910
29
1911
18
1912
27
1913
18
1914
39
1915
22
1916
28
1917
40
1918
25
1919
9
1920
17
1921
30
1922
15
1923
30
1924
17
1925
33
1926
31
1927
35
1928
26
1929
38
1930
71
1931
29
1932
35
1933
23
1934
25
1935
30
1936
31
1937
23
1938
33
1939
26
1940
30
1941
26
1942
23
1943
24
1944
9
1945
25
1946
22
1947
21
1948
25
1949
19
1950
24
All-Time Record Progression
4 new records
4 all-time records were set at Great Falls between 30 September 1924 and 10 July 1936. Each dot is a new record.
When Great Falls set new all-time records
Date
Kind
Detail
1924-09-30
Record daily precipitation
Record daily precipitation 104.1 mm (4.1 in)
1930-07-20
Record high maximum temperature
Record high maximum temperature 40.6 C (105.1 F)
1933-08-24
Record daily precipitation
Record daily precipitation 159.0 mm (6.3 in)
1936-07-10
Record high maximum temperature
Record high maximum temperature 41.1 C (106.0 F)
Wettest Day of Each Month
Aug: 159.0 mm (6.3 in)
The wettest day on record for each calendar month at Great Falls. The most was 159.0 mm (6.3 in) on 24 August 1933.
Record daily precipitation for each month at Great Falls
Month
Record daily precipitation (mm)
Date
Jan
57.2 mm (2.3 in)
13 January 1915
Feb
52.1 mm (2.1 in)
14 February 1936
Mar
51.8 mm (2.0 in)
23 March 1903
Apr
56.9 mm (2.2 in)
9 April 1940
May
66.0 mm (2.6 in)
20 May 1908
Jun
58.9 mm (2.3 in)
30 June 1904
Jul
77.2 mm (3.0 in)
6 July 1945
Aug
159.0 mm (6.3 in)
24 August 1933
Sep
104.1 mm (4.1 in)
30 September 1924
Oct
91.4 mm (3.6 in)
20 October 1906
Nov
75.7 mm (3.0 in)
9 November 1943
Dec
63.5 mm (2.5 in)
29 December 1901
Period of Record Coverage
1897 to 1950
Complete yearUnder 90 percent of days
54 years of record at Great Falls, 1897 to 1950. 9 years have data for under 90 percent of days and are left out of rankings: 1897, 1898, 1906, 1911, 1916, 1918, 1919, 1934 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 38 complete years at Great Falls, 1900 to 1949. Blue stripes are years cooler than the station's own mean of 12.5 C (54.5 F); red stripes are warmer. The coolest year was 1904, at 10.9 C (51.7 F), and the warmest was 1921, at 13.8 C (56.8 F). The strongest colour marks a difference of 1.7 C (3.1 F).
Annual mean temperature at Great Falls as warming stripes, 1900 to 1949
Year
Annual mean temperature
Difference from the station mean
1900
12.5 C
+0.00 C
1902
12.1 C
-0.43 C
1903
11.7 C
-0.86 C
1904
10.9 C
-1.61 C
1905
12.0 C
-0.50 C
1907
11.4 C
-1.14 C
1908
12.6 C
+0.04 C
1909
12.1 C
-0.41 C
1910
12.2 C
-0.34 C
1912
12.0 C
-0.49 C
1915
12.6 C
+0.02 C
1917
11.0 C
-1.53 C
1920
11.9 C
-0.66 C
1921
13.8 C
+1.25 C
1922
13.0 C
+0.50 C
1923
12.7 C
+0.21 C
1924
11.6 C
-0.91 C
1925
12.6 C
+0.06 C
1926
11.8 C
-0.74 C
1927
12.7 C
+0.17 C
1928
12.4 C
-0.11 C
1929
12.6 C
+0.06 C
1930
12.9 C
+0.35 C
1931
13.5 C
+0.92 C
1932
12.9 C
+0.34 C
1933
12.9 C
+0.39 C
1935
12.2 C
-0.34 C
1936
12.5 C
-0.05 C
1937
12.8 C
+0.27 C
1939
13.5 C
+0.95 C
1940
11.9 C
-0.66 C
1941
13.2 C
+0.67 C
1942
13.3 C
+0.72 C
1943
13.0 C
+0.42 C
1945
13.1 C
+0.59 C
1946
13.6 C
+1.11 C
1948
12.9 C
+0.36 C
1949
13.7 C
+1.21 C
The annual mean temperature here has risen by 0.3 C (0.2 to 0.4) per decade over 1900 to 1949. In Fahrenheit: 0.6 F (0.3 to 0.8) per decade. The slope is a straight line fitted to 38 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Great Falls
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.3 C (0.2 to 0.4) per decade
0.6 F (0.3 to 0.8) per decade
1900 to 1949
38
Rise
Mean daily maximum
0.4 C (0.3 to 0.6) per decade
0.7 F (0.5 to 1.0) per decade
1900 to 1949
38
Rise
Mean daily minimum
0.2 C (0.1 to 0.3) per decade
0.4 F (0.1 to 0.6) per decade
1900 to 1949
38
Rise
A year is complete when all 12 months have at least 20 days of both daily maximum and daily minimum readings. The annual mean is the mean of the monthly means. The trend describes this one station over this period; it does not say what caused the change.
Extremes by Year
1893 to 1950
Yearly extremes at Great Falls: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
41.1 C (106.0 F)
1936
36.7 C (98.1 F)
54
Coldest night (TNn)
-29.4 C (-20.9 F)
1912
-16.7 C (1.9 F)
54
Wettest day (Rx1day)
159.0 mm (6.3 in)
1933
57.7 mm (2.3 in)
58
Wettest five days (Rx5day)
217.7 mm (8.6 in)
1937
89.7 mm (3.5 in)
58
Longest dry spell (CDD)
40 days
1901
19 days
58
Hottest day (TXx)
The hottest day of the year at Great Falls, 1893 to 1950. The record is 41.1 C (106.0 F) in 1936, marked on the chart; the median year is 36.7 C (98.1 F).
Hottest day (TXx) at Great Falls by year
Year
Hottest day (TXx)
1893
n/a
1894
n/a
1895
n/a
1896
n/a
1897
35.0 C (95.0 F)
1898
37.8 C (100.0 F)
1899
35.6 C (96.1 F)
1900
37.2 C (99.0 F)
1901
36.1 C (97.0 F)
1902
40.0 C (104.0 F)
1903
37.8 C (100.0 F)
1904
35.6 C (96.1 F)
1905
36.7 C (98.1 F)
1906
36.1 C (97.0 F)
1907
35.6 C (96.1 F)
1908
37.8 C (100.0 F)
1909
37.2 C (99.0 F)
1910
35.6 C (96.1 F)
1911
37.2 C (99.0 F)
1912
35.6 C (96.1 F)
1913
37.2 C (99.0 F)
1914
37.2 C (99.0 F)
1915
36.7 C (98.1 F)
1916
36.1 C (97.0 F)
1917
37.8 C (100.0 F)
1918
34.4 C (93.9 F)
1919
28.9 C (84.0 F)
1920
35.6 C (96.1 F)
1921
36.1 C (97.0 F)
1922
36.1 C (97.0 F)
1923
36.7 C (98.1 F)
1924
38.3 C (100.9 F)
1925
38.3 C (100.9 F)
1926
40.0 C (104.0 F)
1927
35.6 C (96.1 F)
1928
35.6 C (96.1 F)
1929
36.7 C (98.1 F)
1930
40.6 C (105.1 F)
1931
37.8 C (100.0 F)
1932
37.8 C (100.0 F)
1933
37.2 C (99.0 F)
1934
39.4 C (102.9 F)
1935
36.1 C (97.0 F)
1936
41.1 C (106.0 F)
1937
35.6 C (96.1 F)
1938
37.8 C (100.0 F)
1939
37.8 C (100.0 F)
1940
38.9 C (102.0 F)
1941
37.8 C (100.0 F)
1942
36.7 C (98.1 F)
1943
38.3 C (100.9 F)
1944
36.7 C (98.1 F)
1945
38.3 C (100.9 F)
1946
35.0 C (95.0 F)
1947
36.1 C (97.0 F)
1948
37.2 C (99.0 F)
1949
36.1 C (97.0 F)
1950
35.0 C (95.0 F)
Coldest night (TNn)
The coldest night of the year at Great Falls, 1893 to 1950. The record is -29.4 C (-20.9 F) in 1912, marked on the chart; the median year is -16.7 C (1.9 F).
Coldest night (TNn) at Great Falls by year
Year
Coldest night (TNn)
1893
n/a
1894
n/a
1895
n/a
1896
n/a
1897
-12.2 C (10.0 F)
1898
-16.1 C (3.0 F)
1899
-25.6 C (-14.1 F)
1900
-18.9 C (-2.0 F)
1901
-16.7 C (1.9 F)
1902
-17.2 C (1.0 F)
1903
-21.7 C (-7.1 F)
1904
-20.0 C (-4.0 F)
1905
-20.6 C (-5.1 F)
1906
-12.2 C (10.0 F)
1907
-21.1 C (-6.0 F)
1908
-16.1 C (3.0 F)
1909
-14.4 C (6.1 F)
1910
-16.7 C (1.9 F)
1911
-13.9 C (7.0 F)
1912
-29.4 C (-20.9 F)
1913
-12.2 C (10.0 F)
1914
-21.7 C (-7.1 F)
1915
-11.1 C (12.0 F)
1916
-19.4 C (-2.9 F)
1917
-24.4 C (-11.9 F)
1918
-24.4 C (-11.9 F)
1919
-19.4 C (-2.9 F)
1920
-15.0 C (5.0 F)
1921
-14.4 C (6.1 F)
1922
-16.7 C (1.9 F)
1923
-12.2 C (10.0 F)
1924
-15.0 C (5.0 F)
1925
-19.4 C (-2.9 F)
1926
-17.8 C (0.0 F)
1927
-14.4 C (6.1 F)
1928
-20.0 C (-4.0 F)
1929
-15.0 C (5.0 F)
1930
-22.2 C (-8.0 F)
1931
-13.9 C (7.0 F)
1932
-16.7 C (1.9 F)
1933
-16.7 C (1.9 F)
1934
-23.9 C (-11.0 F)
1935
-26.1 C (-15.0 F)
1936
-23.3 C (-9.9 F)
1937
-12.2 C (10.0 F)
1938
-15.0 C (5.0 F)
1939
-12.8 C (9.0 F)
1940
-20.6 C (-5.1 F)
1941
-11.7 C (10.9 F)
1942
-22.2 C (-8.0 F)
1943
-17.8 C (0.0 F)
1944
-12.2 C (10.0 F)
1945
-16.1 C (3.0 F)
1946
-17.8 C (0.0 F)
1947
-17.2 C (1.0 F)
1948
-16.1 C (3.0 F)
1949
-11.1 C (12.0 F)
1950
-13.9 C (7.0 F)
Wettest day (Rx1day)
The wettest day of the year at Great Falls, 1893 to 1950. The record is 159.0 mm (6.3 in) in 1933, marked on the chart; the median year is 57.7 mm (2.3 in).
Wettest day (Rx1day) at Great Falls by year
Year
Wettest day (Rx1day)
1893
66.0 mm (2.6 in)
1894
49.0 mm (1.9 in)
1895
50.8 mm (2.0 in)
1896
40.6 mm (1.6 in)
1897
47.0 mm (1.9 in)
1898
48.3 mm (1.9 in)
1899
56.1 mm (2.2 in)
1900
35.6 mm (1.4 in)
1901
63.5 mm (2.5 in)
1902
70.6 mm (2.8 in)
1903
51.8 mm (2.0 in)
1904
58.9 mm (2.3 in)
1905
63.0 mm (2.5 in)
1906
91.4 mm (3.6 in)
1907
71.9 mm (2.8 in)
1908
90.2 mm (3.6 in)
1909
48.8 mm (1.9 in)
1910
48.3 mm (1.9 in)
1911
40.6 mm (1.6 in)
1912
62.2 mm (2.4 in)
1913
48.8 mm (1.9 in)
1914
45.7 mm (1.8 in)
1915
65.5 mm (2.6 in)
1916
63.8 mm (2.5 in)
1917
64.8 mm (2.6 in)
1918
44.5 mm (1.8 in)
1919
34.5 mm (1.4 in)
1920
65.8 mm (2.6 in)
1921
44.5 mm (1.8 in)
1922
82.6 mm (3.3 in)
1923
76.2 mm (3.0 in)
1924
104.1 mm (4.1 in)
1925
50.3 mm (2.0 in)
1926
71.9 mm (2.8 in)
1927
54.4 mm (2.1 in)
1928
60.5 mm (2.4 in)
1929
76.2 mm (3.0 in)
1930
56.6 mm (2.2 in)
1931
43.2 mm (1.7 in)
1932
65.5 mm (2.6 in)
1933
159.0 mm (6.3 in)
1934
48.5 mm (1.9 in)
1935
72.4 mm (2.9 in)
1936
73.7 mm (2.9 in)
1937
93.7 mm (3.7 in)
1938
45.7 mm (1.8 in)
1939
58.4 mm (2.3 in)
1940
56.9 mm (2.2 in)
1941
45.5 mm (1.8 in)
1942
86.4 mm (3.4 in)
1943
75.7 mm (3.0 in)
1944
83.8 mm (3.3 in)
1945
77.2 mm (3.0 in)
1946
52.6 mm (2.1 in)
1947
44.5 mm (1.8 in)
1948
54.6 mm (2.1 in)
1949
52.8 mm (2.1 in)
1950
44.7 mm (1.8 in)
Wettest five days (Rx5day)
The wettest five days of the year at Great Falls, 1893 to 1950. The record is 217.7 mm (8.6 in) in 1937, marked on the chart; the median year is 89.7 mm (3.5 in).
Wettest five days (Rx5day) at Great Falls by year
Year
Wettest five days (Rx5day)
1893
71.1 mm (2.8 in)
1894
70.4 mm (2.8 in)
1895
87.1 mm (3.4 in)
1896
77.6 mm (3.1 in)
1897
73.5 mm (2.9 in)
1898
90.9 mm (3.6 in)
1899
67.3 mm (2.6 in)
1900
60.4 mm (2.4 in)
1901
119.6 mm (4.7 in)
1902
140.0 mm (5.5 in)
1903
94.4 mm (3.7 in)
1904
121.4 mm (4.8 in)
1905
104.9 mm (4.1 in)
1906
150.9 mm (5.9 in)
1907
102.4 mm (4.0 in)
1908
113.7 mm (4.5 in)
1909
65.0 mm (2.6 in)
1910
82.1 mm (3.2 in)
1911
106.6 mm (4.2 in)
1912
92.4 mm (3.6 in)
1913
84.6 mm (3.3 in)
1914
96.8 mm (3.8 in)
1915
84.2 mm (3.3 in)
1916
166.1 mm (6.5 in)
1917
83.9 mm (3.3 in)
1918
80.9 mm (3.2 in)
1919
66.8 mm (2.6 in)
1920
65.8 mm (2.6 in)
1921
83.3 mm (3.3 in)
1922
107.5 mm (4.2 in)
1923
103.9 mm (4.1 in)
1924
130.0 mm (5.1 in)
1925
98.8 mm (3.9 in)
1926
88.4 mm (3.5 in)
1927
66.5 mm (2.6 in)
1928
110.0 mm (4.3 in)
1929
114.8 mm (4.5 in)
1930
66.2 mm (2.6 in)
1931
51.0 mm (2.0 in)
1932
110.7 mm (4.4 in)
1933
205.0 mm (8.1 in)
1934
70.6 mm (2.8 in)
1935
155.8 mm (6.1 in)
1936
114.4 mm (4.5 in)
1937
217.7 mm (8.6 in)
1938
62.2 mm (2.4 in)
1939
82.2 mm (3.2 in)
1940
73.7 mm (2.9 in)
1941
61.7 mm (2.4 in)
1942
179.9 mm (7.1 in)
1943
81.0 mm (3.2 in)
1944
93.5 mm (3.7 in)
1945
126.2 mm (5.0 in)
1946
81.6 mm (3.2 in)
1947
67.1 mm (2.6 in)
1948
100.8 mm (4.0 in)
1949
120.1 mm (4.7 in)
1950
60.3 mm (2.4 in)
Longest dry spell (CDD)
The longest dry spell of the year at Great Falls, 1893 to 1950. The record is 40 days in 1901, marked on the chart; the median year is 19 days.
Longest dry spell (CDD) at Great Falls by year
Year
Longest dry spell (CDD)
1893
21 days
1894
24 days
1895
24 days
1896
19 days
1897
14 days
1898
34 days
1899
21 days
1900
15 days
1901
40 days
1902
20 days
1903
37 days
1904
20 days
1905
24 days
1906
17 days
1907
19 days
1908
21 days
1909
39 days
1910
24 days
1911
15 days
1912
23 days
1913
15 days
1914
27 days
1915
23 days
1916
13 days
1917
22 days
1918
9 days
1919
10 days
1920
21 days
1921
16 days
1922
25 days
1923
25 days
1924
26 days
1925
13 days
1926
16 days
1927
14 days
1928
17 days
1929
15 days
1930
26 days
1931
28 days
1932
15 days
1933
11 days
1934
15 days
1935
11 days
1936
22 days
1937
20 days
1938
13 days
1939
18 days
1940
14 days
1941
19 days
1942
18 days
1943
18 days
1944
19 days
1945
15 days
1946
21 days
1947
33 days
1948
12 days
1949
26 days
1950
13 days
Each chart shows one value per year; the dot marks the record year. TXx is the hottest daily maximum, TNn the coldest daily minimum, Rx1day and Rx5day the largest one-day and five-day rain totals, and CDD the longest run of days with less than 1 mm of rain. A year with missing days can understate an extreme.
Frost Dates and Growing Season
38 years with a frost
Across 38 years with a frost, the median last spring frost at Great Falls falls on 25 April and the median first autumn frost on 19 October, which leaves a median of 179 days between them.
Fitted over all years, the growing season changes by +0.4 days per decade at this station.
Frost dates and growing season at Great Falls
Measure
Median, all years
Earliest period
Recent period (1910 to 1949)
Recent against earliest
Fitted trend
Last spring frost
25 April
n/a
26 April
n/a
+1.2 days per decade
First autumn frost
19 October
n/a
21 October
n/a
+1.6 days per decade
Growing days
179 days
n/a
180 days
n/a
+0.4 days per decade
A frost day is a day with a daily minimum at or below 0 C (32 F). The last spring frost and the first autumn frost are the last and first such days of the cold season, and growing days are the days between them. A negative trend for the last spring frost means it comes earlier.
Rainfall Return Levels
46 years, 1894 to 1949
A day with at least 58.8 mm (2.3 in) of rain is expected about once in 2 years. A day with at least 131.4 mm (5.2 in) of rain is expected about once in 100 years.
Rainfall return levels at Great Falls: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
58.8 mm (2.3 in)
5 years
75.0 mm (3.0 in)
10 years
86.9 mm (3.4 in)
25 years
103.5 mm (4.1 in)
50 years
117.0 mm (4.6 in)
Longer than the 46 years of record
100 years
131.4 mm (5.2 in)
Longer than the 46 years of record
The levels come from a generalised extreme value (GEV) distribution fitted by L-moments to the wettest-day total of each year, 46 years of values from 1894 to 1949.
A return level is an estimate. It is least reliable for the long periods, 50 and 100 years, and for any period longer than the record behind the fit, where the fit has to reach past the largest day actually observed. It is not a forecast.
The largest wettest-day totals in the fit: 159.0 mm (6.3 in) in 1933; 93.7 mm (3.7 in) in 1937; 90.2 mm (3.6 in) in 1908.
Download the Data
Data for Great Falls standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Great Falls threshold days by year: CSV or JSON. Field meanings are on the data page.
Source: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily). Records are computed by World Extreme Weather Monitor and are not official NOAA products. (US Government open data (NOAA NCEI)) Data as of 2026-10-15 (15 October 2026). Records are computed by this site and are not official.