Record envelope, standing records and threshold days for Port Alsworth (USC00507570), Alaska, United States, with 66 years of record.
Key Facts for Port Alsworth
Port Alsworth (USC00507570) is a weather station in Alaska, United States at 60.20 latitude and -154.32 longitude, 79 m (260 ft) above sea level.
The station reports from 1960 to 2025, 66 years of record.
1,464 records set at Port Alsworth still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Port Alsworth set a daily record high minimum temperature of 4.4 C (39.9 F) on 19 February 2025.
About the Station
Location: Alaska, United States, 60.20 latitude, -154.32 longitude.
Elevation: 79 m (260 ft).
Period of record: 1960 to 2025, 66 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 Port Alsworth. 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 Port Alsworth, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
14.4 C (57.9 F)
-47.2 C (-53.0 F)
7.2 C (45.0 F)
-23.3 C (-9.9 F)
Feb
12.8 C (55.0 F)
-48.3 C (-54.9 F)
8.9 C (48.0 F)
-15.0 C (5.0 F)
Mar
15.0 C (59.0 F)
-45.6 C (-50.1 F)
n/a
n/a
Apr
21.1 C (70.0 F)
-27.8 C (-18.0 F)
n/a
n/a
May
29.4 C (84.9 F)
-10.6 C (12.9 F)
n/a
n/a
Jun
32.2 C (90.0 F)
-6.7 C (19.9 F)
n/a
n/a
Jul
32.8 C (91.0 F)
-3.9 C (25.0 F)
n/a
n/a
Aug
30.6 C (87.1 F)
-5.6 C (21.9 F)
n/a
n/a
Sep
25.0 C (77.0 F)
-10.6 C (12.9 F)
n/a
n/a
Oct
18.9 C (66.0 F)
-21.7 C (-7.1 F)
n/a
n/a
Nov
13.3 C (55.9 F)
-31.1 C (-24.0 F)
n/a
n/a
Dec
11.7 C (53.1 F)
-44.4 C (-47.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Port Alsworth still stand. 1975 holds the most, with 67.
Standing records at Port Alsworth by the year they were set
Year set
Standing records
1960
14
1961
44
1962
29
1963
45
1964
42
1965
48
1966
38
1967
13
1968
44
1969
42
1970
45
1971
47
1972
39
1973
28
1974
28
1975
67
1976
20
1977
13
1978
3
1979
14
1980
18
1981
12
1982
19
1983
10
1984
15
1985
35
1986
18
1987
8
1988
2
1989
24
1990
18
1991
13
1992
25
1993
6
1994
9
1995
18
1996
19
1997
22
1998
12
1999
17
2000
11
2001
15
2002
30
2003
30
2004
28
2005
20
2006
10
2007
7
2008
12
2009
19
2010
16
2011
2
2012
14
2013
30
2014
36
2015
33
2016
36
2017
4
2018
19
2019
51
2020
9
2021
8
2022
19
2023
5
2024
14
2025
3
All-Time Record Progression
9 new records
9 all-time records were set at Port Alsworth between 3 August 1999 and 5 July 2019. Each dot is a new record.
When Port Alsworth set new all-time records
Date
Kind
Detail
1999-08-03
Record high minimum temperature
Record high minimum temperature 17.8 C (64.0 F)
2003-08-08
Record high maximum temperature
Record high maximum temperature 30.6 C (87.1 F)
2004-06-26
Record high maximum temperature
Record high maximum temperature 31.7 C (89.1 F)
2007-12-31
Record daily snowfall
Record daily snowfall 66.0 cm (26.0 in)
2015-06-15
Record high maximum temperature
Record high maximum temperature 32.2 C (90.0 F)
2015-07-06
Record high minimum temperature
Record high minimum temperature 18.3 C (64.9 F)
2018-08-13
Record daily precipitation
Record daily precipitation 67.3 mm (2.6 in)
2019-07-05
Record high maximum temperature
Record high maximum temperature 32.8 C (91.0 F)
2019-07-05
Record high minimum temperature
Record high minimum temperature 20.6 C (69.1 F)
Wettest Day of Each Month
Aug: 67.3 mm (2.6 in)
The wettest day on record for each calendar month at Port Alsworth. The most was 67.3 mm (2.6 in) on 13 August 2018.
Record daily precipitation for each month at Port Alsworth
Month
Record daily precipitation (mm)
Date
Jan
38.6 mm (1.5 in)
16 January 2009
Feb
30.7 mm (1.2 in)
7 February 2003
Mar
17.3 mm (0.7 in)
8 March 1973
Apr
37.6 mm (1.5 in)
21 April 1977
May
29.5 mm (1.2 in)
18 May 1977
Jun
36.3 mm (1.4 in)
20 June 2011
Jul
52.1 mm (2.1 in)
26 July 2019
Aug
67.3 mm (2.6 in)
13 August 2018
Sep
63.5 mm (2.5 in)
10 September 1961
Oct
60.7 mm (2.4 in)
28 October 2013
Nov
63.5 mm (2.5 in)
8 November 2009
Dec
35.6 mm (1.4 in)
26 December 2001
Period of Record Coverage
1960 to 2025
Complete yearUnder 90 percent of days
66 years of record at Port Alsworth, 1960 to 2025. 12 years have data for under 90 percent of days and are left out of rankings: 1960, 2015, 2016, 2017, 2018, 2019, 2020, 2021 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 45 complete years at Port Alsworth, 1961 to 2020. Blue stripes are years cooler than the station's own mean of 1.8 C (35.3 F); red stripes are warmer. The coolest year was 1971, at -1.6 C (29.0 F), and the warmest was 2015, at 5.8 C (42.4 F). The strongest colour marks a difference of 4.0 C (7.2 F).
Annual mean temperature at Port Alsworth as warming stripes, 1961 to 2020
Year
Annual mean temperature
Difference from the station mean
1961
-0.6 C
-2.44 C
1962
1.1 C
-0.71 C
1963
1.5 C
-0.38 C
1964
-0.7 C
-2.49 C
1967
1.4 C
-0.43 C
1968
0.2 C
-1.66 C
1969
1.3 C
-0.55 C
1971
-1.6 C
-3.48 C
1972
-1.3 C
-3.10 C
1973
-0.8 C
-2.67 C
1974
0.2 C
-1.67 C
1975
-1.4 C
-3.27 C
1976
1.0 C
-0.79 C
1977
2.3 C
+0.47 C
1978
4.0 C
+2.16 C
1979
2.3 C
+0.47 C
1980
1.3 C
-0.58 C
1981
4.0 C
+2.21 C
1982
1.5 C
-0.30 C
1983
3.1 C
+1.30 C
1984
2.1 C
+0.30 C
1985
2.1 C
+0.28 C
1986
2.8 C
+0.97 C
1987
2.9 C
+1.02 C
1988
2.8 C
+0.96 C
1989
1.7 C
-0.16 C
1990
1.2 C
-0.63 C
1992
0.6 C
-1.26 C
1994
1.9 C
+0.06 C
1995
2.6 C
+0.76 C
1996
0.8 C
-1.06 C
1997
3.0 C
+1.14 C
1998
2.6 C
+0.80 C
1999
-0.3 C
-2.18 C
2000
3.9 C
+2.04 C
2001
2.9 C
+1.02 C
2002
4.4 C
+2.59 C
2003
4.1 C
+2.24 C
2004
3.7 C
+1.87 C
2005
3.6 C
+1.81 C
2006
1.1 C
-0.75 C
2007
2.2 C
+0.35 C
2011
2.0 C
+0.18 C
2015
5.8 C
+3.94 C
2020
3.4 C
+1.52 C
The annual mean temperature here has risen by 0.7 C (0.4 to 0.9) per decade over 1961 to 2020. In Fahrenheit: 1.2 F (0.7 to 1.7) per decade. The slope is a straight line fitted to 45 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Port Alsworth
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.7 C (0.4 to 0.9) per decade
1.2 F (0.7 to 1.7) per decade
1961 to 2020
45
Rise
Mean daily maximum
0.3 C (0.1 to 0.6) per decade
0.6 F (0.1 to 1.0) per decade
1961 to 2020
45
Rise
Mean daily minimum
1.0 C (0.7 to 1.4) per decade
1.8 F (1.2 to 2.4) per decade
1961 to 2020
45
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
1960 to 2025
Yearly extremes at Port Alsworth: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
32.8 C (91.0 F)
2019
27.8 C (82.0 F)
66
Coldest night (TNn)
-48.3 C (-54.9 F)
1971
-35.6 C (-32.1 F)
66
Wettest day (Rx1day)
67.3 mm (2.6 in)
2018
28.2 mm (1.1 in)
66
Wettest five days (Rx5day)
215.9 mm (8.5 in)
2009
47.2 mm (1.9 in)
66
Longest dry spell (CDD)
66 days
1978
32 days
66
Hottest day (TXx)
The hottest day of the year at Port Alsworth, 1960 to 2025. The record is 32.8 C (91.0 F) in 2019, marked on the chart; the median year is 27.8 C (82.0 F).
Hottest day (TXx) at Port Alsworth by year
Year
Hottest day (TXx)
1960
30.0 C (86.0 F)
1961
23.9 C (75.0 F)
1962
27.8 C (82.0 F)
1963
27.2 C (81.0 F)
1964
25.6 C (78.1 F)
1965
23.9 C (75.0 F)
1966
27.2 C (81.0 F)
1967
29.4 C (84.9 F)
1968
30.0 C (86.0 F)
1969
30.0 C (86.0 F)
1970
26.7 C (80.1 F)
1971
28.3 C (82.9 F)
1972
28.9 C (84.0 F)
1973
24.4 C (75.9 F)
1974
28.3 C (82.9 F)
1975
28.9 C (84.0 F)
1976
27.2 C (81.0 F)
1977
28.3 C (82.9 F)
1978
27.8 C (82.0 F)
1979
25.6 C (78.1 F)
1980
27.8 C (82.0 F)
1981
26.1 C (79.0 F)
1982
24.4 C (75.9 F)
1983
23.9 C (75.0 F)
1984
26.1 C (79.0 F)
1985
23.9 C (75.0 F)
1986
28.3 C (82.9 F)
1987
30.0 C (86.0 F)
1988
26.1 C (79.0 F)
1989
25.6 C (78.1 F)
1990
27.8 C (82.0 F)
1991
23.9 C (75.0 F)
1992
26.7 C (80.1 F)
1993
28.9 C (84.0 F)
1994
25.6 C (78.1 F)
1995
26.7 C (80.1 F)
1996
27.2 C (81.0 F)
1997
29.4 C (84.9 F)
1998
25.6 C (78.1 F)
1999
25.6 C (78.1 F)
2000
28.3 C (82.9 F)
2001
26.7 C (80.1 F)
2002
28.9 C (84.0 F)
2003
30.6 C (87.1 F)
2004
31.7 C (89.1 F)
2005
29.4 C (84.9 F)
2006
29.4 C (84.9 F)
2007
27.2 C (81.0 F)
2008
24.4 C (75.9 F)
2009
29.4 C (84.9 F)
2010
23.9 C (75.0 F)
2011
23.9 C (75.0 F)
2012
27.8 C (82.0 F)
2013
31.7 C (89.1 F)
2014
26.7 C (80.1 F)
2015
32.2 C (90.0 F)
2016
29.4 C (84.9 F)
2017
27.2 C (81.0 F)
2018
29.4 C (84.9 F)
2019
32.8 C (91.0 F)
2020
27.8 C (82.0 F)
2021
27.8 C (82.0 F)
2022
27.8 C (82.0 F)
2023
26.1 C (79.0 F)
2024
29.4 C (84.9 F)
2025
8.9 C (48.0 F)
Coldest night (TNn)
The coldest night of the year at Port Alsworth, 1960 to 2025. The record is -48.3 C (-54.9 F) in 1971, marked on the chart; the median year is -35.6 C (-32.1 F).
Coldest night (TNn) at Port Alsworth by year
Year
Coldest night (TNn)
1960
-25.6 C (-14.1 F)
1961
-38.9 C (-38.0 F)
1962
-35.6 C (-32.1 F)
1963
-34.4 C (-29.9 F)
1964
-37.8 C (-36.0 F)
1965
-41.1 C (-42.0 F)
1966
-45.6 C (-50.1 F)
1967
-38.3 C (-36.9 F)
1968
-45.6 C (-50.1 F)
1969
-45.6 C (-50.1 F)
1970
-34.4 C (-29.9 F)
1971
-48.3 C (-54.9 F)
1972
-40.0 C (-40.0 F)
1973
-47.2 C (-53.0 F)
1974
-36.7 C (-34.1 F)
1975
-42.8 C (-45.0 F)
1976
-32.8 C (-27.0 F)
1977
-37.2 C (-35.0 F)
1978
-30.0 C (-22.0 F)
1979
-34.4 C (-29.9 F)
1980
-41.1 C (-42.0 F)
1981
-25.0 C (-13.0 F)
1982
-35.0 C (-31.0 F)
1983
-31.7 C (-25.1 F)
1984
-41.1 C (-42.0 F)
1985
-35.0 C (-31.0 F)
1986
-31.1 C (-24.0 F)
1987
-32.2 C (-26.0 F)
1988
-26.1 C (-15.0 F)
1989
-45.6 C (-50.1 F)
1990
-39.4 C (-38.9 F)
1991
-40.0 C (-40.0 F)
1992
-38.3 C (-36.9 F)
1993
-38.9 C (-38.0 F)
1994
-31.7 C (-25.1 F)
1995
-35.0 C (-31.0 F)
1996
-40.0 C (-40.0 F)
1997
-43.3 C (-45.9 F)
1998
-34.4 C (-29.9 F)
1999
-42.8 C (-45.0 F)
2000
-40.0 C (-40.0 F)
2001
-37.8 C (-36.0 F)
2002
-30.0 C (-22.0 F)
2003
-30.6 C (-23.1 F)
2004
-37.8 C (-36.0 F)
2005
-30.6 C (-23.1 F)
2006
-41.1 C (-42.0 F)
2007
-37.8 C (-36.0 F)
2008
-38.9 C (-38.0 F)
2009
-41.1 C (-42.0 F)
2010
-34.4 C (-29.9 F)
2011
-35.6 C (-32.1 F)
2012
-28.3 C (-18.9 F)
2013
-27.8 C (-18.0 F)
2014
-25.0 C (-13.0 F)
2015
-26.1 C (-15.0 F)
2016
-22.2 C (-8.0 F)
2017
-36.1 C (-33.0 F)
2018
-23.9 C (-11.0 F)
2019
-26.1 C (-15.0 F)
2020
-33.9 C (-29.0 F)
2021
-27.2 C (-17.0 F)
2022
-30.6 C (-23.1 F)
2023
-24.4 C (-11.9 F)
2024
-38.9 C (-38.0 F)
2025
-23.3 C (-9.9 F)
Wettest day (Rx1day)
The wettest day of the year at Port Alsworth, 1960 to 2025. The record is 67.3 mm (2.6 in) in 2018, marked on the chart; the median year is 28.2 mm (1.1 in).
Wettest day (Rx1day) at Port Alsworth by year
Year
Wettest day (Rx1day)
1960
22.1 mm (0.9 in)
1961
63.5 mm (2.5 in)
1962
19.6 mm (0.8 in)
1963
35.3 mm (1.4 in)
1964
29.0 mm (1.1 in)
1965
19.6 mm (0.8 in)
1966
21.1 mm (0.8 in)
1967
61.0 mm (2.4 in)
1968
17.3 mm (0.7 in)
1969
26.9 mm (1.1 in)
1970
33.0 mm (1.3 in)
1971
57.2 mm (2.3 in)
1972
19.1 mm (0.8 in)
1973
32.3 mm (1.3 in)
1974
16.3 mm (0.6 in)
1975
29.2 mm (1.1 in)
1976
27.9 mm (1.1 in)
1977
37.6 mm (1.5 in)
1978
15.5 mm (0.6 in)
1979
34.3 mm (1.4 in)
1980
17.3 mm (0.7 in)
1981
43.7 mm (1.7 in)
1982
34.5 mm (1.4 in)
1983
40.9 mm (1.6 in)
1984
20.3 mm (0.8 in)
1985
27.9 mm (1.1 in)
1986
30.7 mm (1.2 in)
1987
23.9 mm (0.9 in)
1988
20.8 mm (0.8 in)
1989
6.1 mm (0.24 in)
1990
17.5 mm (0.7 in)
1991
10.7 mm (0.4 in)
1992
10.7 mm (0.4 in)
1993
11.4 mm (0.4 in)
1994
13.2 mm (0.5 in)
1995
15.7 mm (0.6 in)
1996
27.9 mm (1.1 in)
1997
15.5 mm (0.6 in)
1998
15.5 mm (0.6 in)
1999
15.5 mm (0.6 in)
2000
25.4 mm (1.0 in)
2001
35.6 mm (1.4 in)
2002
48.0 mm (1.9 in)
2003
33.3 mm (1.3 in)
2004
28.4 mm (1.1 in)
2005
34.3 mm (1.4 in)
2006
17.0 mm (0.7 in)
2007
48.8 mm (1.9 in)
2008
25.1 mm (1.0 in)
2009
63.5 mm (2.5 in)
2010
32.5 mm (1.3 in)
2011
36.3 mm (1.4 in)
2012
26.2 mm (1.0 in)
2013
60.7 mm (2.4 in)
2014
29.5 mm (1.2 in)
2015
38.9 mm (1.5 in)
2016
45.7 mm (1.8 in)
2017
23.1 mm (0.9 in)
2018
67.3 mm (2.6 in)
2019
52.1 mm (2.1 in)
2020
33.0 mm (1.3 in)
2021
31.8 mm (1.3 in)
2022
33.5 mm (1.3 in)
2023
41.1 mm (1.6 in)
2024
10.7 mm (0.4 in)
2025
0.5 mm (0.02 in)
Wettest five days (Rx5day)
The wettest five days of the year at Port Alsworth, 1960 to 2025. The record is 215.9 mm (8.5 in) in 2009, marked on the chart; the median year is 47.2 mm (1.9 in).
Wettest five days (Rx5day) at Port Alsworth by year
Year
Wettest five days (Rx5day)
1960
38.1 mm (1.5 in)
1961
111.0 mm (4.4 in)
1962
57.3 mm (2.3 in)
1963
85.5 mm (3.4 in)
1964
45.6 mm (1.8 in)
1965
48.5 mm (1.9 in)
1966
36.3 mm (1.4 in)
1967
95.5 mm (3.8 in)
1968
34.3 mm (1.4 in)
1969
37.1 mm (1.5 in)
1970
45.3 mm (1.8 in)
1971
169.4 mm (6.7 in)
1972
43.5 mm (1.7 in)
1973
75.7 mm (3.0 in)
1974
34.2 mm (1.3 in)
1975
51.8 mm (2.0 in)
1976
54.9 mm (2.2 in)
1977
65.3 mm (2.6 in)
1978
27.4 mm (1.1 in)
1979
49.7 mm (2.0 in)
1980
37.2 mm (1.5 in)
1981
57.2 mm (2.3 in)
1982
72.9 mm (2.9 in)
1983
84.3 mm (3.3 in)
1984
49.6 mm (2.0 in)
1985
70.3 mm (2.8 in)
1986
55.3 mm (2.2 in)
1987
43.5 mm (1.7 in)
1988
33.3 mm (1.3 in)
1989
14.8 mm (0.6 in)
1990
34.1 mm (1.3 in)
1991
23.6 mm (0.9 in)
1992
16.0 mm (0.6 in)
1993
21.7 mm (0.9 in)
1994
27.4 mm (1.1 in)
1995
20.6 mm (0.8 in)
1996
33.0 mm (1.3 in)
1997
31.8 mm (1.3 in)
1998
40.7 mm (1.6 in)
1999
31.5 mm (1.2 in)
2000
28.7 mm (1.1 in)
2001
46.0 mm (1.8 in)
2002
72.7 mm (2.9 in)
2003
50.2 mm (2.0 in)
2004
47.3 mm (1.9 in)
2005
51.1 mm (2.0 in)
2006
36.0 mm (1.4 in)
2007
61.5 mm (2.4 in)
2008
40.9 mm (1.6 in)
2009
215.9 mm (8.5 in)
2010
42.1 mm (1.7 in)
2011
49.8 mm (2.0 in)
2012
52.3 mm (2.1 in)
2013
83.0 mm (3.3 in)
2014
33.1 mm (1.3 in)
2015
52.5 mm (2.1 in)
2016
46.7 mm (1.8 in)
2017
53.6 mm (2.1 in)
2018
92.2 mm (3.6 in)
2019
75.0 mm (3.0 in)
2020
67.2 mm (2.6 in)
2021
78.8 mm (3.1 in)
2022
47.0 mm (1.9 in)
2023
54.3 mm (2.1 in)
2024
10.7 mm (0.4 in)
2025
0.5 mm (0.02 in)
Longest dry spell (CDD)
The longest dry spell of the year at Port Alsworth, 1960 to 2025. The record is 66 days in 1978, marked on the chart; the median year is 32 days.
Longest dry spell (CDD) at Port Alsworth by year
Year
Longest dry spell (CDD)
1960
15 days
1961
20 days
1962
34 days
1963
32 days
1964
27 days
1965
30 days
1966
19 days
1967
49 days
1968
50 days
1969
59 days
1970
39 days
1971
40 days
1972
47 days
1973
51 days
1974
23 days
1975
30 days
1976
28 days
1977
21 days
1978
66 days
1979
33 days
1980
46 days
1981
20 days
1982
36 days
1983
32 days
1984
35 days
1985
35 days
1986
62 days
1987
30 days
1988
29 days
1989
35 days
1990
45 days
1991
41 days
1992
48 days
1993
51 days
1994
49 days
1995
30 days
1996
41 days
1997
52 days
1998
38 days
1999
35 days
2000
35 days
2001
32 days
2002
25 days
2003
30 days
2004
21 days
2005
24 days
2006
41 days
2007
49 days
2008
20 days
2009
30 days
2010
32 days
2011
52 days
2012
28 days
2013
40 days
2014
49 days
2015
20 days
2016
15 days
2017
13 days
2018
29 days
2019
25 days
2020
23 days
2021
32 days
2022
29 days
2023
26 days
2024
32 days
2025
24 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
45 years with a frost
Across 45 years with a frost, the median last spring frost at Port Alsworth falls on 27 May and the median first autumn frost on 4 September, which leaves a median of 106 days between them.
Fitted over all years, the growing season changes by +18.5 days per decade at this station.
Frost dates and growing season at Port Alsworth
Measure
Median, all years
Earliest period
Recent period (1979 to 2020)
Recent against earliest
Fitted trend
Last spring frost
27 May
n/a
22 May
n/a
-6.8 days per decade
First autumn frost
4 September
n/a
10 September
n/a
+11.7 days per decade
Growing days
106 days
n/a
118 days
n/a
+18.5 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
53 years, 1961 to 2020
A day with at least 26.4 mm (1.0 in) of rain is expected about once in 2 years. A day with at least 76.7 mm (3.0 in) of rain is expected about once in 100 years.
Rainfall return levels at Port Alsworth: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
26.4 mm (1.0 in)
5 years
39.2 mm (1.5 in)
10 years
48.0 mm (1.9 in)
25 years
59.3 mm (2.3 in)
50 years
68.0 mm (2.7 in)
100 years
76.7 mm (3.0 in)
Longer than the 53 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, 53 years of values from 1961 to 2020.
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: 63.5 mm (2.5 in) in 1961; 63.5 mm (2.5 in) in 2009; 61.0 mm (2.4 in) in 1967.
Station Changes
1 suspected
One change was suspected in the annual mean temperature of Port Alsworth, at 1976. Each is measured against neighbouring stations.
Relative to 5 neighbouring stations, the station's annual mean temperature from 1976 ran 0.9 C (1.6 F) higher than in the years before (likely change).
Suspected changes in the annual mean temperature at Port Alsworth, against neighbouring stations
Year
Shift (C)
Shift (F)
Strength
Neighbours
1976
+0.9
+1.6
likely
5
Possible change at the station (a move, a new instrument or a new site); the record is kept as measured. A "likely" change has a larger test statistic than a "possible" one. Neither says why the station differs from its neighbours. How changes are found, and the largest ones.
Download the Data
Data for Port Alsworth standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Port Alsworth 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.