Record envelope, standing records and threshold days for Arrowrock Dam (USC00100448), Idaho, United States, with 99 years of record.
Key Facts for Arrowrock Dam
Arrowrock Dam (USC00100448) is a weather station in Idaho, United States at 43.59 latitude and -115.92 longitude, 986 m (3,235 ft) above sea level.
The station reports from 1911 to 2009, 99 years of record.
1,464 records set at Arrowrock Dam still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Arrowrock Dam set a daily record low maximum temperature of 6.7 C (44.1 F) on 4 October 2009.
About the Station
Location: Idaho, United States, 43.59 latitude, -115.92 longitude.
Elevation: 986 m (3,235 ft).
Period of record: 1911 to 2009, 99 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.
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 Arrowrock Dam. 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 Arrowrock Dam, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
13.3 C (55.9 F)
-35.6 C (-32.1 F)
n/a
n/a
Feb
19.4 C (66.9 F)
-28.9 C (-20.0 F)
n/a
n/a
Mar
27.2 C (81.0 F)
-18.3 C (-0.9 F)
n/a
n/a
Apr
33.3 C (91.9 F)
-13.3 C (8.1 F)
n/a
n/a
May
36.7 C (98.1 F)
-6.1 C (21.0 F)
n/a
n/a
Jun
42.2 C (108.0 F)
-5.6 C (21.9 F)
n/a
n/a
Jul
44.4 C (111.9 F)
2.8 C (37.0 F)
n/a
n/a
Aug
42.8 C (109.0 F)
1.7 C (35.1 F)
n/a
n/a
Sep
40.6 C (105.1 F)
-6.1 C (21.0 F)
n/a
n/a
Oct
34.4 C (93.9 F)
-8.9 C (16.0 F)
n/a
n/a
Nov
22.8 C (73.0 F)
-21.1 C (-6.0 F)
n/a
n/a
Dec
16.7 C (62.1 F)
-30.0 C (-22.0 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Arrowrock Dam still stand. 1917 holds the most, with 37.
Standing records at Arrowrock Dam by the year they were set
Year set
Standing records
1912
22
1913
21
1914
25
1915
25
1916
20
1917
37
1918
25
1919
27
1920
14
1921
14
1922
20
1923
7
1924
28
1925
16
1926
27
1927
15
1928
11
1929
20
1930
32
1931
33
1932
15
1933
21
1934
32
1935
20
1936
20
1937
17
1938
8
1939
14
1940
21
1941
7
1942
11
1943
13
1944
7
1945
10
1946
4
1947
13
1948
7
1949
36
1950
20
1951
10
1952
13
1953
14
1954
13
1955
22
1956
12
1957
12
1958
11
1959
14
1960
17
1961
19
1962
12
1963
19
1964
17
1965
24
1966
13
1967
4
1968
17
1969
17
1970
19
1971
13
1972
13
1973
5
1974
14
1975
17
1976
1
1977
14
1978
14
1979
8
1980
7
1981
5
1982
6
1983
15
1984
6
1985
12
1986
15
1987
13
1988
5
1989
8
1990
17
1991
1
1992
20
1993
12
1994
11
1995
16
1996
8
1997
8
1998
13
1999
26
2000
9
2001
14
2002
13
2003
24
2004
2
2005
13
2006
11
2007
5
2008
8
2009
8
All-Time Record Progression
1 new records
1 all-time records were set at Arrowrock Dam between 15 February 1949 and 15 February 1949. Each dot is a new record.
When Arrowrock Dam set new all-time records
Date
Kind
Detail
1949-02-15
Record daily snowfall
Record daily snowfall 45.7 cm (18.0 in)
Wettest Day of Each Month
Feb: 78.7 mm (3.1 in)
The wettest day on record for each calendar month at Arrowrock Dam. The most was 78.7 mm (3.1 in) on 2 February 1916.
Record daily precipitation for each month at Arrowrock Dam
Month
Record daily precipitation (mm)
Date
Jan
55.9 mm (2.2 in)
18 January 1953
Feb
78.7 mm (3.1 in)
2 February 1916
Mar
30.5 mm (1.2 in)
29 March 1913
Apr
34.8 mm (1.4 in)
14 April 1973
May
32.0 mm (1.3 in)
29 May 1990
Jun
36.6 mm (1.4 in)
30 June 1938
Jul
35.6 mm (1.4 in)
24 July 1913
Aug
27.4 mm (1.1 in)
12 August 1941
Sep
42.9 mm (1.7 in)
26 September 1959
Oct
48.0 mm (1.9 in)
7 October 1913
Nov
52.1 mm (2.1 in)
27 November 1971
Dec
49.0 mm (1.9 in)
28 December 1945
Period of Record Coverage
1911 to 2009
Complete yearUnder 90 percent of days
99 years of record at Arrowrock Dam, 1911 to 2009. 23 years have data for under 90 percent of days and are left out of rankings: 1911, 1915, 1916, 1917, 1927, 1929, 1985, 1986 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 76 complete years at Arrowrock Dam, 1912 to 2003. Blue stripes are years cooler than the station's own mean of 9.5 C (49.1 F); red stripes are warmer. The coolest year was 1955, at 8.0 C (46.3 F), and the warmest was 1934, at 12.0 C (53.5 F). The strongest colour marks a difference of 2.5 C (4.5 F).
Annual mean temperature at Arrowrock Dam as warming stripes, 1912 to 2003
Year
Annual mean temperature
Difference from the station mean
1912
9.4 C
-0.12 C
1913
9.6 C
+0.07 C
1914
11.0 C
+1.47 C
1918
10.3 C
+0.75 C
1919
9.4 C
-0.15 C
1920
9.6 C
+0.07 C
1921
10.1 C
+0.58 C
1922
9.0 C
-0.47 C
1923
9.2 C
-0.34 C
1924
9.6 C
+0.04 C
1925
10.2 C
+0.70 C
1926
11.0 C
+1.45 C
1928
9.4 C
-0.08 C
1929
8.6 C
-0.89 C
1930
8.8 C
-0.75 C
1931
9.6 C
+0.09 C
1932
8.5 C
-1.00 C
1933
8.9 C
-0.59 C
1934
12.0 C
+2.44 C
1935
8.8 C
-0.71 C
1936
9.1 C
-0.37 C
1938
9.7 C
+0.16 C
1939
9.7 C
+0.16 C
1940
10.8 C
+1.25 C
1941
10.4 C
+0.88 C
1942
8.7 C
-0.82 C
1943
9.2 C
-0.34 C
1944
8.9 C
-0.65 C
1945
9.0 C
-0.48 C
1946
9.0 C
-0.53 C
1947
9.7 C
+0.14 C
1948
8.4 C
-1.09 C
1949
8.3 C
-1.20 C
1950
9.3 C
-0.24 C
1951
8.7 C
-0.77 C
1952
9.0 C
-0.51 C
1953
10.0 C
+0.50 C
1954
9.7 C
+0.16 C
1955
8.0 C
-1.56 C
1956
9.0 C
-0.54 C
1957
9.1 C
-0.37 C
1958
10.6 C
+1.08 C
1959
10.3 C
+0.80 C
1960
10.1 C
+0.59 C
1961
10.6 C
+1.12 C
1962
9.7 C
+0.17 C
1963
10.5 C
+0.95 C
1964
8.3 C
-1.17 C
1965
9.7 C
+0.16 C
1966
10.2 C
+0.72 C
1967
10.0 C
+0.46 C
1968
9.3 C
-0.26 C
1969
9.5 C
-0.06 C
1970
8.9 C
-0.61 C
1971
8.6 C
-0.88 C
1972
8.9 C
-0.66 C
1973
9.9 C
+0.40 C
1974
9.1 C
-0.45 C
1975
8.2 C
-1.35 C
1977
8.9 C
-0.60 C
1978
9.1 C
-0.40 C
1979
9.3 C
-0.23 C
1980
9.7 C
+0.18 C
1981
10.2 C
+0.72 C
1982
8.4 C
-1.15 C
1983
9.9 C
+0.35 C
1984
8.1 C
-1.45 C
1989
8.9 C
-0.59 C
1990
9.7 C
+0.23 C
1991
9.2 C
-0.31 C
1992
10.7 C
+1.22 C
1993
8.5 C
-1.06 C
1994
10.6 C
+1.05 C
1998
10.7 C
+1.14 C
1999
11.0 C
+1.47 C
2003
11.6 C
+2.13 C
The fitted trend in annual mean temperature here over 1912 to 2003 is 0.01 C (-0.07 to 0.09) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: 0.02 F (-0.12 to 0.17) per decade. The slope is a straight line fitted to 76 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Arrowrock Dam
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.01 C (-0.07 to 0.09) per decade
0.02 F (-0.12 to 0.17) per decade
1912 to 2003
76
Not clearly different from zero
Mean daily maximum
-0.06 C (-0.15 to 0.04) per decade
-0.1 F (-0.3 to 0.1) per decade
1912 to 2003
76
Not clearly different from zero
Mean daily minimum
0.08 C (0.00 to 0.17) per decade
0.15 F (0.00 to 0.30) per decade
1912 to 2003
76
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
1911 to 2009
Yearly extremes at Arrowrock Dam: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
44.4 C (111.9 F)
1934
39.4 C (102.9 F)
99
Coldest night (TNn)
-35.6 C (-32.1 F)
1937
-18.9 C (-2.0 F)
99
Wettest day (Rx1day)
78.7 mm (3.1 in)
1916
31.8 mm (1.3 in)
99
Wettest five days (Rx5day)
166.4 mm (6.6 in)
1916
59.0 mm (2.3 in)
99
Longest dry spell (CDD)
133 days
1935
46 days
99
Hottest day (TXx)
The hottest day of the year at Arrowrock Dam, 1911 to 2009. The record is 44.4 C (111.9 F) in 1934, marked on the chart; the median year is 39.4 C (102.9 F).
Hottest day (TXx) at Arrowrock Dam by year
Year
Hottest day (TXx)
1911
11.1 C (52.0 F)
1912
38.3 C (100.9 F)
1913
38.9 C (102.0 F)
1914
38.3 C (100.9 F)
1915
40.0 C (104.0 F)
1916
37.8 C (100.0 F)
1917
40.0 C (104.0 F)
1918
38.9 C (102.0 F)
1919
40.0 C (104.0 F)
1920
40.6 C (105.1 F)
1921
38.3 C (100.9 F)
1922
38.9 C (102.0 F)
1923
37.8 C (100.0 F)
1924
41.1 C (106.0 F)
1925
40.0 C (104.0 F)
1926
40.6 C (105.1 F)
1927
37.8 C (100.0 F)
1928
41.7 C (107.1 F)
1929
42.2 C (108.0 F)
1930
40.0 C (104.0 F)
1931
43.3 C (109.9 F)
1932
39.4 C (102.9 F)
1933
42.2 C (108.0 F)
1934
44.4 C (111.9 F)
1935
41.1 C (106.0 F)
1936
42.2 C (108.0 F)
1937
37.2 C (99.0 F)
1938
38.3 C (100.9 F)
1939
40.0 C (104.0 F)
1940
42.2 C (108.0 F)
1941
39.4 C (102.9 F)
1942
40.6 C (105.1 F)
1943
40.6 C (105.1 F)
1944
38.3 C (100.9 F)
1945
37.8 C (100.0 F)
1946
40.0 C (104.0 F)
1947
38.3 C (100.9 F)
1948
37.2 C (99.0 F)
1949
40.0 C (104.0 F)
1950
40.6 C (105.1 F)
1951
40.0 C (104.0 F)
1952
37.8 C (100.0 F)
1953
40.0 C (104.0 F)
1954
37.8 C (100.0 F)
1955
39.4 C (102.9 F)
1956
40.0 C (104.0 F)
1957
37.2 C (99.0 F)
1958
38.9 C (102.0 F)
1959
41.1 C (106.0 F)
1960
42.8 C (109.0 F)
1961
42.8 C (109.0 F)
1962
37.8 C (100.0 F)
1963
37.8 C (100.0 F)
1964
37.8 C (100.0 F)
1965
37.8 C (100.0 F)
1966
39.4 C (102.9 F)
1967
39.4 C (102.9 F)
1968
40.0 C (104.0 F)
1969
39.4 C (102.9 F)
1970
37.2 C (99.0 F)
1971
38.9 C (102.0 F)
1972
38.3 C (100.9 F)
1973
40.0 C (104.0 F)
1974
38.9 C (102.0 F)
1975
40.0 C (104.0 F)
1976
37.8 C (100.0 F)
1977
38.3 C (100.9 F)
1978
38.9 C (102.0 F)
1979
39.4 C (102.9 F)
1980
40.6 C (105.1 F)
1981
38.3 C (100.9 F)
1982
38.3 C (100.9 F)
1983
41.7 C (107.1 F)
1984
37.8 C (100.0 F)
1985
39.4 C (102.9 F)
1986
39.4 C (102.9 F)
1987
38.3 C (100.9 F)
1988
39.4 C (102.9 F)
1989
41.1 C (106.0 F)
1990
42.2 C (108.0 F)
1991
39.4 C (102.9 F)
1992
40.0 C (104.0 F)
1993
37.8 C (100.0 F)
1994
41.1 C (106.0 F)
1995
42.2 C (108.0 F)
1996
40.0 C (104.0 F)
1997
38.9 C (102.0 F)
1998
40.6 C (105.1 F)
1999
38.3 C (100.9 F)
2000
40.6 C (105.1 F)
2001
41.1 C (106.0 F)
2002
41.1 C (106.0 F)
2003
40.6 C (105.1 F)
2004
38.9 C (102.0 F)
2005
40.6 C (105.1 F)
2006
40.0 C (104.0 F)
2007
25.6 C (78.1 F)
2008
38.9 C (102.0 F)
2009
38.9 C (102.0 F)
Coldest night (TNn)
The coldest night of the year at Arrowrock Dam, 1911 to 2009. The record is -35.6 C (-32.1 F) in 1937, marked on the chart; the median year is -18.9 C (-2.0 F).
Coldest night (TNn) at Arrowrock Dam by year
Year
Coldest night (TNn)
1911
-12.8 C (9.0 F)
1912
-22.2 C (-8.0 F)
1913
-22.2 C (-8.0 F)
1914
-18.3 C (-0.9 F)
1915
-25.6 C (-14.1 F)
1916
-21.7 C (-7.1 F)
1917
-21.7 C (-7.1 F)
1918
-17.2 C (1.0 F)
1919
-26.1 C (-15.0 F)
1920
-17.8 C (0.0 F)
1921
-16.7 C (1.9 F)
1922
-29.4 C (-20.9 F)
1923
-22.2 C (-8.0 F)
1924
-30.0 C (-22.0 F)
1925
-17.8 C (0.0 F)
1926
-20.6 C (-5.1 F)
1927
-26.1 C (-15.0 F)
1928
-18.3 C (-0.9 F)
1929
-23.9 C (-11.0 F)
1930
-30.6 C (-23.1 F)
1931
-24.4 C (-11.9 F)
1932
-21.1 C (-6.0 F)
1933
-28.9 C (-20.0 F)
1934
-11.7 C (10.9 F)
1935
-27.2 C (-17.0 F)
1936
-25.0 C (-13.0 F)
1937
-35.6 C (-32.1 F)
1938
-11.7 C (10.9 F)
1939
-21.1 C (-6.0 F)
1940
-15.0 C (5.0 F)
1941
-13.9 C (7.0 F)
1942
-22.8 C (-9.0 F)
1943
-23.9 C (-11.0 F)
1944
-15.6 C (3.9 F)
1945
-18.9 C (-2.0 F)
1946
-16.7 C (1.9 F)
1947
-27.8 C (-18.0 F)
1948
-25.6 C (-14.1 F)
1949
-28.9 C (-20.0 F)
1950
-28.9 C (-20.0 F)
1951
-22.2 C (-8.0 F)
1952
-18.9 C (-2.0 F)
1953
-10.6 C (12.9 F)
1954
-15.0 C (5.0 F)
1955
-21.1 C (-6.0 F)
1956
-24.4 C (-11.9 F)
1957
-28.9 C (-20.0 F)
1958
-12.8 C (9.0 F)
1959
-17.8 C (0.0 F)
1960
-18.3 C (-0.9 F)
1961
-17.2 C (1.0 F)
1962
-28.3 C (-18.9 F)
1963
-22.8 C (-9.0 F)
1964
-22.2 C (-8.0 F)
1965
-13.3 C (8.1 F)
1966
-11.7 C (10.9 F)
1967
-16.1 C (3.0 F)
1968
-15.0 C (5.0 F)
1969
-12.8 C (9.0 F)
1970
-16.1 C (3.0 F)
1971
-21.1 C (-6.0 F)
1972
-23.3 C (-9.9 F)
1973
-12.8 C (9.0 F)
1974
-23.9 C (-11.0 F)
1975
-15.6 C (3.9 F)
1976
-17.2 C (1.0 F)
1977
-17.2 C (1.0 F)
1978
-20.6 C (-5.1 F)
1979
-24.4 C (-11.9 F)
1980
-20.6 C (-5.1 F)
1981
-12.8 C (9.0 F)
1982
-22.2 C (-8.0 F)
1983
-22.2 C (-8.0 F)
1984
-21.7 C (-7.1 F)
1985
-24.4 C (-11.9 F)
1986
-15.0 C (5.0 F)
1987
-15.6 C (3.9 F)
1988
-22.2 C (-8.0 F)
1989
-26.7 C (-16.1 F)
1990
-27.8 C (-18.0 F)
1991
-18.3 C (-0.9 F)
1992
-18.9 C (-2.0 F)
1993
-18.3 C (-0.9 F)
1994
-15.0 C (5.0 F)
1995
-15.6 C (3.9 F)
1996
-23.3 C (-9.9 F)
1997
-13.9 C (7.0 F)
1998
-19.4 C (-2.9 F)
1999
-11.1 C (12.0 F)
2000
-11.1 C (12.0 F)
2001
-20.0 C (-4.0 F)
2002
-16.7 C (1.9 F)
2003
-8.9 C (16.0 F)
2004
-16.7 C (1.9 F)
2005
-11.7 C (10.9 F)
2006
-13.3 C (8.1 F)
2007
-14.4 C (6.1 F)
2008
-18.9 C (-2.0 F)
2009
-8.9 C (16.0 F)
Wettest day (Rx1day)
The wettest day of the year at Arrowrock Dam, 1911 to 2009. The record is 78.7 mm (3.1 in) in 1916, marked on the chart; the median year is 31.8 mm (1.3 in).
Wettest day (Rx1day) at Arrowrock Dam by year
Year
Wettest day (Rx1day)
1911
18.3 mm (0.7 in)
1912
39.4 mm (1.6 in)
1913
48.0 mm (1.9 in)
1914
21.1 mm (0.8 in)
1915
30.5 mm (1.2 in)
1916
78.7 mm (3.1 in)
1917
40.6 mm (1.6 in)
1918
17.8 mm (0.7 in)
1919
35.6 mm (1.4 in)
1920
21.6 mm (0.9 in)
1921
45.7 mm (1.8 in)
1922
17.8 mm (0.7 in)
1923
34.3 mm (1.4 in)
1924
44.5 mm (1.8 in)
1925
35.6 mm (1.4 in)
1926
29.0 mm (1.1 in)
1927
45.0 mm (1.8 in)
1928
26.7 mm (1.1 in)
1929
20.3 mm (0.8 in)
1930
45.7 mm (1.8 in)
1931
20.3 mm (0.8 in)
1932
29.0 mm (1.1 in)
1933
17.8 mm (0.7 in)
1934
27.9 mm (1.1 in)
1935
21.6 mm (0.9 in)
1936
27.4 mm (1.1 in)
1937
38.1 mm (1.5 in)
1938
48.8 mm (1.9 in)
1939
23.4 mm (0.9 in)
1940
22.6 mm (0.9 in)
1941
34.3 mm (1.4 in)
1942
43.2 mm (1.7 in)
1943
27.7 mm (1.1 in)
1944
28.7 mm (1.1 in)
1945
49.0 mm (1.9 in)
1946
25.7 mm (1.0 in)
1947
23.1 mm (0.9 in)
1948
38.1 mm (1.5 in)
1949
31.8 mm (1.3 in)
1950
33.0 mm (1.3 in)
1951
38.4 mm (1.5 in)
1952
24.1 mm (0.9 in)
1953
55.9 mm (2.2 in)
1954
40.4 mm (1.6 in)
1955
25.9 mm (1.0 in)
1956
34.0 mm (1.3 in)
1957
42.7 mm (1.7 in)
1958
32.8 mm (1.3 in)
1959
42.9 mm (1.7 in)
1960
26.9 mm (1.1 in)
1961
37.6 mm (1.5 in)
1962
21.8 mm (0.9 in)
1963
40.6 mm (1.6 in)
1964
34.8 mm (1.4 in)
1965
29.5 mm (1.2 in)
1966
19.1 mm (0.8 in)
1967
21.1 mm (0.8 in)
1968
31.8 mm (1.3 in)
1969
29.5 mm (1.2 in)
1970
36.8 mm (1.4 in)
1971
52.1 mm (2.1 in)
1972
38.1 mm (1.5 in)
1973
34.8 mm (1.4 in)
1974
21.1 mm (0.8 in)
1975
38.9 mm (1.5 in)
1976
36.3 mm (1.4 in)
1977
31.8 mm (1.3 in)
1978
26.4 mm (1.0 in)
1979
28.2 mm (1.1 in)
1980
41.4 mm (1.6 in)
1981
38.1 mm (1.5 in)
1982
35.6 mm (1.4 in)
1983
27.7 mm (1.1 in)
1984
20.3 mm (0.8 in)
1985
34.3 mm (1.4 in)
1986
33.0 mm (1.3 in)
1987
23.6 mm (0.9 in)
1988
27.2 mm (1.1 in)
1989
37.3 mm (1.5 in)
1990
32.5 mm (1.3 in)
1991
30.5 mm (1.2 in)
1992
23.1 mm (0.9 in)
1993
26.2 mm (1.0 in)
1994
25.1 mm (1.0 in)
1995
24.4 mm (1.0 in)
1996
33.3 mm (1.3 in)
1997
29.2 mm (1.1 in)
1998
53.1 mm (2.1 in)
1999
43.9 mm (1.7 in)
2000
24.4 mm (1.0 in)
2001
32.5 mm (1.3 in)
2002
32.5 mm (1.3 in)
2003
27.9 mm (1.1 in)
2004
25.1 mm (1.0 in)
2005
22.9 mm (0.9 in)
2006
15.7 mm (0.6 in)
2007
22.6 mm (0.9 in)
2008
49.3 mm (1.9 in)
2009
26.7 mm (1.1 in)
Wettest five days (Rx5day)
The wettest five days of the year at Arrowrock Dam, 1911 to 2009. The record is 166.4 mm (6.6 in) in 1916, marked on the chart; the median year is 59.0 mm (2.3 in).
Wettest five days (Rx5day) at Arrowrock Dam by year
Year
Wettest five days (Rx5day)
1911
37.6 mm (1.5 in)
1912
70.5 mm (2.8 in)
1913
72.2 mm (2.8 in)
1914
62.5 mm (2.5 in)
1915
67.1 mm (2.6 in)
1916
166.4 mm (6.6 in)
1917
67.3 mm (2.6 in)
1918
48.3 mm (1.9 in)
1919
68.5 mm (2.7 in)
1920
43.0 mm (1.7 in)
1921
113.8 mm (4.5 in)
1922
33.3 mm (1.3 in)
1923
70.5 mm (2.8 in)
1924
59.0 mm (2.3 in)
1925
66.6 mm (2.6 in)
1926
55.6 mm (2.2 in)
1927
85.2 mm (3.4 in)
1928
51.1 mm (2.0 in)
1929
54.1 mm (2.1 in)
1930
59.7 mm (2.4 in)
1931
47.0 mm (1.9 in)
1932
79.9 mm (3.1 in)
1933
35.9 mm (1.4 in)
1934
41.3 mm (1.6 in)
1935
43.2 mm (1.7 in)
1936
59.8 mm (2.4 in)
1937
56.1 mm (2.2 in)
1938
72.1 mm (2.8 in)
1939
34.5 mm (1.4 in)
1940
46.5 mm (1.8 in)
1941
43.8 mm (1.7 in)
1942
82.6 mm (3.3 in)
1943
71.3 mm (2.8 in)
1944
42.9 mm (1.7 in)
1945
82.8 mm (3.3 in)
1946
55.4 mm (2.2 in)
1947
32.5 mm (1.3 in)
1948
66.8 mm (2.6 in)
1949
81.2 mm (3.2 in)
1950
63.4 mm (2.5 in)
1951
80.1 mm (3.2 in)
1952
49.6 mm (2.0 in)
1953
119.8 mm (4.7 in)
1954
47.8 mm (1.9 in)
1955
75.0 mm (3.0 in)
1956
60.3 mm (2.4 in)
1957
73.8 mm (2.9 in)
1958
59.5 mm (2.3 in)
1959
47.0 mm (1.9 in)
1960
68.7 mm (2.7 in)
1961
58.6 mm (2.3 in)
1962
36.6 mm (1.4 in)
1963
80.0 mm (3.1 in)
1964
95.8 mm (3.8 in)
1965
73.1 mm (2.9 in)
1966
47.5 mm (1.9 in)
1967
46.5 mm (1.8 in)
1968
81.5 mm (3.2 in)
1969
71.9 mm (2.8 in)
1970
89.7 mm (3.5 in)
1971
83.1 mm (3.3 in)
1972
102.9 mm (4.1 in)
1973
52.6 mm (2.1 in)
1974
39.9 mm (1.6 in)
1975
57.4 mm (2.3 in)
1976
73.9 mm (2.9 in)
1977
64.7 mm (2.5 in)
1978
38.2 mm (1.5 in)
1979
45.0 mm (1.8 in)
1980
57.7 mm (2.3 in)
1981
59.4 mm (2.3 in)
1982
86.5 mm (3.4 in)
1983
60.4 mm (2.4 in)
1984
48.3 mm (1.9 in)
1985
41.6 mm (1.6 in)
1986
82.0 mm (3.2 in)
1987
27.4 mm (1.1 in)
1988
49.2 mm (1.9 in)
1989
75.7 mm (3.0 in)
1990
52.1 mm (2.1 in)
1991
64.0 mm (2.5 in)
1992
50.4 mm (2.0 in)
1993
70.2 mm (2.8 in)
1994
51.5 mm (2.0 in)
1995
49.8 mm (2.0 in)
1996
60.2 mm (2.4 in)
1997
43.7 mm (1.7 in)
1998
103.9 mm (4.1 in)
1999
64.7 mm (2.5 in)
2000
44.7 mm (1.8 in)
2001
48.1 mm (1.9 in)
2002
38.9 mm (1.5 in)
2003
55.9 mm (2.2 in)
2004
44.4 mm (1.7 in)
2005
47.0 mm (1.9 in)
2006
34.5 mm (1.4 in)
2007
18.5 mm (0.7 in)
2008
65.1 mm (2.6 in)
2009
36.5 mm (1.4 in)
Longest dry spell (CDD)
The longest dry spell of the year at Arrowrock Dam, 1911 to 2009. The record is 133 days in 1935, marked on the chart; the median year is 46 days.
Longest dry spell (CDD) at Arrowrock Dam by year
Year
Longest dry spell (CDD)
1911
19 days
1912
27 days
1913
43 days
1914
53 days
1915
53 days
1916
45 days
1917
104 days
1918
55 days
1919
110 days
1920
39 days
1921
85 days
1922
41 days
1923
32 days
1924
91 days
1925
34 days
1926
40 days
1927
26 days
1928
37 days
1929
45 days
1930
60 days
1931
57 days
1932
40 days
1933
106 days
1934
33 days
1935
133 days
1936
91 days
1937
41 days
1938
75 days
1939
40 days
1940
29 days
1941
21 days
1942
69 days
1943
94 days
1944
86 days
1945
31 days
1946
59 days
1947
73 days
1948
79 days
1949
52 days
1950
31 days
1951
38 days
1952
116 days
1953
60 days
1954
36 days
1955
54 days
1956
43 days
1957
109 days
1958
35 days
1959
54 days
1960
64 days
1961
50 days
1962
50 days
1963
39 days
1964
35 days
1965
40 days
1966
95 days
1967
63 days
1968
50 days
1969
65 days
1970
37 days
1971
40 days
1972
40 days
1973
62 days
1974
50 days
1975
25 days
1976
28 days
1977
39 days
1978
58 days
1979
52 days
1980
70 days
1981
44 days
1982
26 days
1983
24 days
1984
31 days
1985
55 days
1986
44 days
1987
78 days
1988
43 days
1989
37 days
1990
39 days
1991
46 days
1992
72 days
1993
49 days
1994
69 days
1995
47 days
1996
29 days
1997
27 days
1998
38 days
1999
74 days
2000
44 days
2001
36 days
2002
80 days
2003
56 days
2004
49 days
2005
80 days
2006
78 days
2007
28 days
2008
41 days
2009
30 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
76 years with a frost
Across 76 years with a frost, the median last spring frost at Arrowrock Dam falls on 4 May and the median first autumn frost on 10 October, which leaves a median of 156 days between them.
In 1963 to 2003 the median growing season was 154 days. That is 6 days fewer than in 1912 to 1946.
Fitted over all years, the growing season changes by +0.5 days per decade at this station.
Frost dates and growing season at Arrowrock Dam
Measure
Median, all years
Earliest period (1912 to 1946)
Recent period (1963 to 2003)
Recent against earliest
Fitted trend
Last spring frost
4 May
6 May
6 May
no change
-0.5 days per decade
First autumn frost
10 October
11 October
8 October
3 days earlier
0.0 days per decade
Growing days
156 days
160 days
154 days
6 days fewer
+0.5 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
90 years, 1912 to 2004
A day with at least 31.3 mm (1.2 in) of rain is expected about once in 2 years. A day with at least 63.5 mm (2.5 in) of rain is expected about once in 100 years.
Rainfall return levels at Arrowrock Dam: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
31.3 mm (1.2 in)
5 years
40.3 mm (1.6 in)
10 years
46.1 mm (1.8 in)
25 years
53.3 mm (2.1 in)
50 years
58.5 mm (2.3 in)
100 years
63.5 mm (2.5 in)
Longer than the 90 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, 90 years of values from 1912 to 2004.
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: 78.7 mm (3.1 in) in 1916; 55.9 mm (2.2 in) in 1953; 53.1 mm (2.1 in) in 1998.
Station Changes
No change in the annual mean temperature of this station was found against its neighbours.
Download the Data
Data for Arrowrock Dam standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Arrowrock Dam 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 2026-10-14 (14 October 2026). Records are computed by this site and are not official.