Record highRecord low2026 daily maximum2026 daily minimum
The band shows the record high and record low for each calendar day at Harrow Cda. 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 Harrow Cda, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
17.2 C (63.0 F)
-26.1 C (-15.0 F)
n/a
n/a
Feb
19.4 C (66.9 F)
-28.9 C (-20.0 F)
n/a
n/a
Mar
26.1 C (79.0 F)
-20.6 C (-5.1 F)
n/a
n/a
Apr
30.0 C (86.0 F)
-12.5 C (9.5 F)
n/a
n/a
May
33.9 C (93.0 F)
-3.9 C (25.0 F)
n/a
n/a
Jun
37.2 C (99.0 F)
1.7 C (35.1 F)
n/a
n/a
Jul
40.6 C (105.1 F)
5.6 C (42.1 F)
n/a
n/a
Aug
40.0 C (104.0 F)
3.9 C (39.0 F)
n/a
n/a
Sep
36.7 C (98.1 F)
-2.2 C (28.0 F)
n/a
n/a
Oct
32.2 C (90.0 F)
-6.1 C (21.0 F)
n/a
n/a
Nov
25.6 C (78.1 F)
-15.6 C (3.9 F)
n/a
n/a
Dec
17.2 C (63.0 F)
-27.0 C (-16.6 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Harrow Cda still stand. 1933 holds the most, with 40.
Standing records at Harrow Cda by the year they were set
Year set
Standing records
1917
30
1918
35
1919
13
1920
28
1921
28
1922
15
1923
26
1924
22
1925
32
1926
24
1927
24
1928
19
1929
28
1930
37
1931
28
1932
25
1933
40
1934
25
1935
23
1936
32
1937
16
1938
19
1939
20
1940
20
1941
20
1942
34
1943
17
1944
26
1945
35
1946
24
1947
19
1948
10
1949
25
1950
33
1951
28
1952
12
1953
21
1954
16
1955
13
1956
14
1957
15
1958
13
1959
19
1960
17
1961
8
1962
23
1963
29
1964
24
1965
24
1966
10
1967
27
1968
13
1969
13
1970
12
1971
10
1972
17
1973
12
1974
20
1975
19
1976
28
1977
30
1978
17
1979
28
1980
8
1981
16
1982
31
1983
25
All-Time Record Progression
6 new records
6 all-time records were set at Harrow Cda between 7 July 1957 and 24 December 1983. Each dot is a new record.
When Harrow Cda set new all-time records
Date
Kind
Detail
1957-07-07
Record daily precipitation
Record daily precipitation 74.4 mm (2.9 in)
1972-01-15
Record low maximum temperature
Record low maximum temperature -18.9 C (-2.0 F)
1974-12-01
Record daily snowfall
Record daily snowfall 39.4 cm (15.5 in)
1982-03-03
Record daily snowfall
Record daily snowfall 44.0 cm (17.3 in)
1983-05-01
Record daily precipitation
Record daily precipitation 88.5 mm (3.5 in)
1983-12-24
Record low maximum temperature
Record low maximum temperature -19.0 C (-2.2 F)
Wettest Day of Each Month
May: 88.5 mm (3.5 in)
The wettest day on record for each calendar month at Harrow Cda. The most was 88.5 mm (3.5 in) on 1 May 1983.
Record daily precipitation for each month at Harrow Cda
Month
Record daily precipitation (mm)
Date
Jan
44.5 mm (1.8 in)
26 January 1978
Feb
55.6 mm (2.2 in)
29 February 1976
Mar
44.0 mm (1.7 in)
3 March 1982
Apr
58.4 mm (2.3 in)
22 April 1977
May
88.5 mm (3.5 in)
1 May 1983
Jun
57.2 mm (2.3 in)
25 June 1968
Jul
74.4 mm (2.9 in)
7 July 1957
Aug
64.3 mm (2.5 in)
14 August 1972
Sep
57.7 mm (2.3 in)
23 September 1926
Oct
61.2 mm (2.4 in)
6 October 1959
Nov
56.3 mm (2.2 in)
1 November 1982
Dec
49.8 mm (2.0 in)
24 December 1965
Period of Record Coverage
1917 to 1983
Complete yearUnder 90 percent of days
67 years of record at Harrow Cda, 1917 to 1983. 1 years have data for under 90 percent of days and are left out of rankings: 1917.
Cooler than the station meanWarmer than the station mean
One stripe for each of 65 complete years at Harrow Cda, 1918 to 1983. Blue stripes are years cooler than the station's own mean of 9.3 C (48.8 F); red stripes are warmer. The coolest year was 1978, at 8.0 C (46.3 F), and the warmest was 1946, at 11.0 C (51.8 F). The strongest colour marks a difference of 1.7 C (3.1 F).
Annual mean temperature at Harrow Cda as warming stripes, 1918 to 1983
Year
Annual mean temperature
Difference from the station mean
1918
9.1 C
-0.26 C
1919
9.6 C
+0.27 C
1920
8.4 C
-0.97 C
1921
11.0 C
+1.69 C
1922
9.8 C
+0.44 C
1923
9.1 C
-0.26 C
1924
8.1 C
-1.22 C
1925
8.8 C
-0.56 C
1926
8.1 C
-1.23 C
1927
9.3 C
-0.02 C
1928
9.3 C
+0.01 C
1929
8.4 C
-0.94 C
1930
9.5 C
+0.18 C
1931
11.0 C
+1.64 C
1932
9.9 C
+0.56 C
1933
10.3 C
+1.02 C
1934
9.5 C
+0.18 C
1935
8.9 C
-0.41 C
1936
9.0 C
-0.37 C
1937
9.0 C
-0.31 C
1938
10.3 C
+0.98 C
1939
10.3 C
+1.00 C
1940
8.8 C
-0.56 C
1941
10.6 C
+1.29 C
1942
9.9 C
+0.53 C
1943
9.3 C
-0.06 C
1944
10.3 C
+1.02 C
1945
9.5 C
+0.18 C
1946
11.0 C
+1.70 C
1947
9.9 C
+0.60 C
1948
9.8 C
+0.43 C
1949
10.8 C
+1.51 C
1950
8.9 C
-0.44 C
1951
9.3 C
-0.05 C
1952
10.4 C
+1.05 C
1953
10.8 C
+1.43 C
1954
9.9 C
+0.60 C
1955
10.0 C
+0.72 C
1956
9.0 C
-0.31 C
1958
8.3 C
-1.07 C
1959
9.1 C
-0.23 C
1960
8.7 C
-0.64 C
1961
9.3 C
-0.05 C
1962
8.9 C
-0.41 C
1963
8.4 C
-0.96 C
1964
9.5 C
+0.13 C
1965
9.0 C
-0.35 C
1966
8.8 C
-0.56 C
1967
8.8 C
-0.51 C
1968
9.3 C
-0.06 C
1969
8.7 C
-0.61 C
1970
8.9 C
-0.39 C
1971
9.5 C
+0.22 C
1972
8.5 C
-0.85 C
1973
10.2 C
+0.85 C
1974
9.1 C
-0.23 C
1975
9.7 C
+0.36 C
1976
8.5 C
-0.85 C
1977
8.9 C
-0.39 C
1978
8.0 C
-1.36 C
1979
8.2 C
-1.15 C
1980
8.4 C
-0.92 C
1981
8.8 C
-0.48 C
1982
8.9 C
-0.47 C
1983
9.5 C
+0.22 C
The annual mean temperature here has fallen by 0.10 C (0.00 to 0.20) per decade over 1918 to 1983. In Fahrenheit: 0.18 F (0.00 to 0.36) per decade. The slope is a straight line fitted to 65 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Harrow Cda
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
-0.10 C (-0.20 to 0.00) per decade
-0.18 F (-0.36 to 0.00) per decade
1918 to 1983
65
Fall
Mean daily maximum
-0.3 C (-0.4 to -0.2) per decade
-0.5 F (-0.7 to -0.3) per decade
1918 to 1983
65
Fall
Mean daily minimum
0.08 C (-0.02 to 0.17) per decade
0.14 F (-0.03 to 0.31) per decade
1918 to 1983
65
Not clearly different from zero
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
1917 to 1983
Yearly extremes at Harrow Cda: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
40.6 C (105.1 F)
1936
34.4 C (93.9 F)
67
Coldest night (TNn)
-28.9 C (-20.0 F)
1918
-20.6 C (-5.1 F)
67
Wettest day (Rx1day)
88.5 mm (3.5 in)
1983
42.7 mm (1.7 in)
67
Wettest five days (Rx5day)
148.9 mm (5.9 in)
1957
63.4 mm (2.5 in)
67
Longest dry spell (CDD)
35 days
1924
19 days
67
Hottest day (TXx)
The hottest day of the year at Harrow Cda, 1917 to 1983. The record is 40.6 C (105.1 F) in 1936, marked on the chart; the median year is 34.4 C (93.9 F).
Hottest day (TXx) at Harrow Cda by year
Year
Hottest day (TXx)
1917
35.6 C (96.1 F)
1918
40.0 C (104.0 F)
1919
35.6 C (96.1 F)
1920
33.3 C (91.9 F)
1921
36.1 C (97.0 F)
1922
34.4 C (93.9 F)
1923
35.0 C (95.0 F)
1924
34.4 C (93.9 F)
1925
36.7 C (98.1 F)
1926
37.2 C (99.0 F)
1927
36.7 C (98.1 F)
1928
34.4 C (93.9 F)
1929
33.9 C (93.0 F)
1930
37.2 C (99.0 F)
1931
36.7 C (98.1 F)
1932
36.7 C (98.1 F)
1933
37.2 C (99.0 F)
1934
37.2 C (99.0 F)
1935
37.2 C (99.0 F)
1936
40.6 C (105.1 F)
1937
33.9 C (93.0 F)
1938
33.3 C (91.9 F)
1939
35.0 C (95.0 F)
1940
35.6 C (96.1 F)
1941
35.6 C (96.1 F)
1942
36.1 C (97.0 F)
1943
35.6 C (96.1 F)
1944
37.2 C (99.0 F)
1945
34.4 C (93.9 F)
1946
37.8 C (100.0 F)
1947
36.1 C (97.0 F)
1948
35.6 C (96.1 F)
1949
35.6 C (96.1 F)
1950
34.4 C (93.9 F)
1951
33.9 C (93.0 F)
1952
37.2 C (99.0 F)
1953
37.2 C (99.0 F)
1954
36.1 C (97.0 F)
1955
36.1 C (97.0 F)
1956
32.8 C (91.0 F)
1957
31.7 C (89.1 F)
1958
31.7 C (89.1 F)
1959
32.2 C (90.0 F)
1960
33.9 C (93.0 F)
1961
32.8 C (91.0 F)
1962
33.9 C (93.0 F)
1963
33.9 C (93.0 F)
1964
33.9 C (93.0 F)
1965
33.3 C (91.9 F)
1966
35.0 C (95.0 F)
1967
33.9 C (93.0 F)
1968
32.8 C (91.0 F)
1969
32.2 C (90.0 F)
1970
33.3 C (91.9 F)
1971
35.0 C (95.0 F)
1972
32.8 C (91.0 F)
1973
34.4 C (93.9 F)
1974
33.9 C (93.0 F)
1975
33.3 C (91.9 F)
1976
33.9 C (93.0 F)
1977
33.1 C (91.6 F)
1978
35.0 C (95.0 F)
1979
31.0 C (87.8 F)
1980
33.0 C (91.4 F)
1981
33.0 C (91.4 F)
1982
32.0 C (89.6 F)
1983
34.5 C (94.1 F)
Coldest night (TNn)
The coldest night of the year at Harrow Cda, 1917 to 1983. The record is -28.9 C (-20.0 F) in 1918, marked on the chart; the median year is -20.6 C (-5.1 F).
Coldest night (TNn) at Harrow Cda by year
Year
Coldest night (TNn)
1917
-22.8 C (-9.0 F)
1918
-28.9 C (-20.0 F)
1919
-18.3 C (-0.9 F)
1920
-23.3 C (-9.9 F)
1921
-14.4 C (6.1 F)
1922
-21.1 C (-6.0 F)
1923
-18.9 C (-2.0 F)
1924
-23.9 C (-11.0 F)
1925
-23.3 C (-9.9 F)
1926
-19.4 C (-2.9 F)
1927
-25.6 C (-14.1 F)
1928
-18.3 C (-0.9 F)
1929
-24.4 C (-11.9 F)
1930
-24.4 C (-11.9 F)
1931
-16.1 C (3.0 F)
1932
-20.6 C (-5.1 F)
1933
-22.8 C (-9.0 F)
1934
-27.2 C (-17.0 F)
1935
-20.0 C (-4.0 F)
1936
-22.2 C (-8.0 F)
1937
-19.4 C (-2.9 F)
1938
-18.9 C (-2.0 F)
1939
-19.4 C (-2.9 F)
1940
-23.3 C (-9.9 F)
1941
-15.6 C (3.9 F)
1942
-20.6 C (-5.1 F)
1943
-20.6 C (-5.1 F)
1944
-21.7 C (-7.1 F)
1945
-21.1 C (-6.0 F)
1946
-16.7 C (1.9 F)
1947
-16.7 C (1.9 F)
1948
-23.3 C (-9.9 F)
1949
-13.9 C (7.0 F)
1950
-20.0 C (-4.0 F)
1951
-21.1 C (-6.0 F)
1952
-13.3 C (8.1 F)
1953
-14.4 C (6.1 F)
1954
-17.2 C (1.0 F)
1955
-16.7 C (1.9 F)
1956
-16.7 C (1.9 F)
1957
-21.1 C (-6.0 F)
1958
-22.2 C (-8.0 F)
1959
-18.9 C (-2.0 F)
1960
-20.0 C (-4.0 F)
1961
-23.3 C (-9.9 F)
1962
-22.2 C (-8.0 F)
1963
-26.1 C (-15.0 F)
1964
-17.8 C (0.0 F)
1965
-21.7 C (-7.1 F)
1966
-20.6 C (-5.1 F)
1967
-18.3 C (-0.9 F)
1968
-21.1 C (-6.0 F)
1969
-18.9 C (-2.0 F)
1970
-22.8 C (-9.0 F)
1971
-20.6 C (-5.1 F)
1972
-23.3 C (-9.9 F)
1973
-18.9 C (-2.0 F)
1974
-19.4 C (-2.9 F)
1975
-20.0 C (-4.0 F)
1976
-22.2 C (-8.0 F)
1977
-23.3 C (-9.9 F)
1978
-20.0 C (-4.0 F)
1979
-23.5 C (-10.3 F)
1980
-18.5 C (-1.3 F)
1981
-24.5 C (-12.1 F)
1982
-26.0 C (-14.8 F)
1983
-27.0 C (-16.6 F)
Wettest day (Rx1day)
The wettest day of the year at Harrow Cda, 1917 to 1983. The record is 88.5 mm (3.5 in) in 1983, marked on the chart; the median year is 42.7 mm (1.7 in).
Wettest day (Rx1day) at Harrow Cda by year
Year
Wettest day (Rx1day)
1917
46.0 mm (1.8 in)
1918
38.9 mm (1.5 in)
1919
44.2 mm (1.7 in)
1920
47.2 mm (1.9 in)
1921
50.8 mm (2.0 in)
1922
35.1 mm (1.4 in)
1923
37.1 mm (1.5 in)
1924
34.3 mm (1.4 in)
1925
27.2 mm (1.1 in)
1926
57.7 mm (2.3 in)
1927
28.2 mm (1.1 in)
1928
26.9 mm (1.1 in)
1929
38.1 mm (1.5 in)
1930
19.6 mm (0.8 in)
1931
23.6 mm (0.9 in)
1932
34.8 mm (1.4 in)
1933
16.5 mm (0.6 in)
1934
43.7 mm (1.7 in)
1935
36.1 mm (1.4 in)
1936
36.1 mm (1.4 in)
1937
56.9 mm (2.2 in)
1938
37.8 mm (1.5 in)
1939
53.6 mm (2.1 in)
1940
41.4 mm (1.6 in)
1941
39.6 mm (1.6 in)
1942
42.7 mm (1.7 in)
1943
32.8 mm (1.3 in)
1944
34.3 mm (1.4 in)
1945
49.0 mm (1.9 in)
1946
33.3 mm (1.3 in)
1947
49.0 mm (1.9 in)
1948
36.6 mm (1.4 in)
1949
40.6 mm (1.6 in)
1950
30.5 mm (1.2 in)
1951
47.2 mm (1.9 in)
1952
53.6 mm (2.1 in)
1953
37.8 mm (1.5 in)
1954
57.7 mm (2.3 in)
1955
38.6 mm (1.5 in)
1956
42.7 mm (1.7 in)
1957
74.4 mm (2.9 in)
1958
28.7 mm (1.1 in)
1959
61.2 mm (2.4 in)
1960
32.8 mm (1.3 in)
1961
41.1 mm (1.6 in)
1962
56.1 mm (2.2 in)
1963
34.3 mm (1.4 in)
1964
47.5 mm (1.9 in)
1965
49.8 mm (2.0 in)
1966
71.6 mm (2.8 in)
1967
48.5 mm (1.9 in)
1968
57.2 mm (2.3 in)
1969
68.8 mm (2.7 in)
1970
46.7 mm (1.8 in)
1971
36.3 mm (1.4 in)
1972
64.3 mm (2.5 in)
1973
50.8 mm (2.0 in)
1974
39.4 mm (1.6 in)
1975
46.0 mm (1.8 in)
1976
55.6 mm (2.2 in)
1977
58.4 mm (2.3 in)
1978
44.5 mm (1.8 in)
1979
38.5 mm (1.5 in)
1980
40.0 mm (1.6 in)
1981
45.8 mm (1.8 in)
1982
56.3 mm (2.2 in)
1983
88.5 mm (3.5 in)
Wettest five days (Rx5day)
The wettest five days of the year at Harrow Cda, 1917 to 1983. The record is 148.9 mm (5.9 in) in 1957, marked on the chart; the median year is 63.4 mm (2.5 in).
Wettest five days (Rx5day) at Harrow Cda by year
Year
Wettest five days (Rx5day)
1917
72.9 mm (2.9 in)
1918
56.2 mm (2.2 in)
1919
55.7 mm (2.2 in)
1920
86.3 mm (3.4 in)
1921
56.4 mm (2.2 in)
1922
51.8 mm (2.0 in)
1923
43.7 mm (1.7 in)
1924
51.1 mm (2.0 in)
1925
52.6 mm (2.1 in)
1926
81.5 mm (3.2 in)
1927
42.0 mm (1.7 in)
1928
40.4 mm (1.6 in)
1929
52.3 mm (2.1 in)
1930
33.9 mm (1.3 in)
1931
34.5 mm (1.4 in)
1932
65.3 mm (2.6 in)
1933
31.2 mm (1.2 in)
1934
46.5 mm (1.8 in)
1935
62.5 mm (2.5 in)
1936
50.1 mm (2.0 in)
1937
76.7 mm (3.0 in)
1938
85.3 mm (3.4 in)
1939
99.6 mm (3.9 in)
1940
71.6 mm (2.8 in)
1941
57.7 mm (2.3 in)
1942
77.4 mm (3.0 in)
1943
51.6 mm (2.0 in)
1944
40.6 mm (1.6 in)
1945
81.7 mm (3.2 in)
1946
45.8 mm (1.8 in)
1947
86.5 mm (3.4 in)
1948
80.0 mm (3.1 in)
1949
62.7 mm (2.5 in)
1950
56.1 mm (2.2 in)
1951
48.8 mm (1.9 in)
1952
63.4 mm (2.5 in)
1953
42.7 mm (1.7 in)
1954
76.3 mm (3.0 in)
1955
62.5 mm (2.5 in)
1956
64.3 mm (2.5 in)
1957
148.9 mm (5.9 in)
1958
50.9 mm (2.0 in)
1959
93.8 mm (3.7 in)
1960
59.1 mm (2.3 in)
1961
87.0 mm (3.4 in)
1962
64.7 mm (2.5 in)
1963
52.1 mm (2.1 in)
1964
72.4 mm (2.9 in)
1965
62.8 mm (2.5 in)
1966
133.4 mm (5.3 in)
1967
61.2 mm (2.4 in)
1968
103.9 mm (4.1 in)
1969
111.2 mm (4.4 in)
1970
53.3 mm (2.1 in)
1971
47.3 mm (1.9 in)
1972
121.7 mm (4.8 in)
1973
66.8 mm (2.6 in)
1974
63.0 mm (2.5 in)
1975
80.1 mm (3.2 in)
1976
116.6 mm (4.6 in)
1977
102.5 mm (4.0 in)
1978
64.3 mm (2.5 in)
1979
69.8 mm (2.7 in)
1980
75.3 mm (3.0 in)
1981
69.4 mm (2.7 in)
1982
82.7 mm (3.3 in)
1983
127.9 mm (5.0 in)
Longest dry spell (CDD)
The longest dry spell of the year at Harrow Cda, 1917 to 1983. The record is 35 days in 1924, marked on the chart; the median year is 19 days.
Longest dry spell (CDD) at Harrow Cda by year
Year
Longest dry spell (CDD)
1917
27 days
1918
24 days
1919
26 days
1920
23 days
1921
19 days
1922
27 days
1923
22 days
1924
35 days
1925
23 days
1926
15 days
1927
21 days
1928
19 days
1929
19 days
1930
27 days
1931
19 days
1932
19 days
1933
21 days
1934
20 days
1935
14 days
1936
21 days
1937
15 days
1938
15 days
1939
19 days
1940
12 days
1941
22 days
1942
22 days
1943
18 days
1944
35 days
1945
23 days
1946
18 days
1947
24 days
1948
18 days
1949
21 days
1950
13 days
1951
15 days
1952
21 days
1953
22 days
1954
15 days
1955
17 days
1956
20 days
1957
23 days
1958
15 days
1959
12 days
1960
17 days
1961
23 days
1962
14 days
1963
31 days
1964
21 days
1965
16 days
1966
16 days
1967
17 days
1968
18 days
1969
35 days
1970
17 days
1971
16 days
1972
14 days
1973
17 days
1974
14 days
1975
15 days
1976
27 days
1977
13 days
1978
25 days
1979
16 days
1980
15 days
1981
16 days
1982
11 days
1983
16 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
65 years with a frost
Across 65 years with a frost, the median last spring frost at Harrow Cda falls on 3 May and the median first autumn frost on 15 October, which leaves a median of 166 days between them.
In 1953 to 1983 the median growing season was 168 days. That is 5 days more than in 1918 to 1947.
Fitted over all years, the growing season changes by +1.9 days per decade at this station.
Frost dates and growing season at Harrow Cda
Measure
Median, all years
Earliest period (1918 to 1947)
Recent period (1953 to 1983)
Recent against earliest
Fitted trend
Last spring frost
3 May
11 May
29 April
12 days earlier
-1.8 days per decade
First autumn frost
15 October
13 October
16 October
3 days later
+0.1 days per decade
Growing days
166 days
163 days
168 days
5 days more
+1.9 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
65 years, 1918 to 1983
A day with at least 42.8 mm (1.7 in) of rain is expected about once in 2 years. A day with at least 81.8 mm (3.2 in) of rain is expected about once in 100 years.
Rainfall return levels at Harrow Cda: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
42.8 mm (1.7 in)
5 years
54.5 mm (2.1 in)
10 years
61.7 mm (2.4 in)
25 years
70.2 mm (2.8 in)
50 years
76.2 mm (3.0 in)
100 years
81.8 mm (3.2 in)
Longer than the 65 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, 65 years of values from 1918 to 1983.
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: 88.5 mm (3.5 in) in 1983; 74.4 mm (2.9 in) in 1957; 71.6 mm (2.8 in) in 1966.
Station Changes
No change in the annual mean temperature of this station was found against its neighbours.
Download the Data
Data for Harrow Cda standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Harrow Cda 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 2026-10-12 (12 October 2026). Records are computed by this site and are not official.