Record envelope, standing records and threshold days for Portland (USC00176902), Maine, United States, with 70 years of record.
Key Facts for Portland
Portland (USC00176902) is a weather station in Maine, United States at 43.65 latitude and -70.25 longitude, n/a above sea level.
The station reports from 1871 to 1940, 70 years of record.
1,464 records set at Portland still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Portland tied a daily record low maximum temperature of 6.1 C (43.0 F) on 22 October 1940.
About the Station
Location: Maine, United States, 43.65 latitude, -70.25 longitude.
Elevation: n/a.
Period of record: 1871 to 1940, 70 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 Portland. 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 Portland, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
18.3 C (64.9 F)
-27.8 C (-18.0 F)
n/a
n/a
Feb
14.4 C (57.9 F)
-27.8 C (-18.0 F)
n/a
n/a
Mar
26.1 C (79.0 F)
-20.0 C (-4.0 F)
n/a
n/a
Apr
31.7 C (89.1 F)
-12.8 C (9.0 F)
n/a
n/a
May
35.6 C (96.1 F)
-2.8 C (27.0 F)
n/a
n/a
Jun
35.6 C (96.1 F)
3.3 C (37.9 F)
n/a
n/a
Jul
39.4 C (102.9 F)
8.9 C (48.0 F)
n/a
n/a
Aug
36.7 C (98.1 F)
6.7 C (44.1 F)
n/a
n/a
Sep
35.6 C (96.1 F)
0.0 C (32.0 F)
n/a
n/a
Oct
29.4 C (84.9 F)
-5.6 C (21.9 F)
n/a
n/a
Nov
23.3 C (73.9 F)
-21.1 C (-6.0 F)
n/a
n/a
Dec
18.3 C (64.9 F)
-29.4 C (-20.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Portland still stand. 1888 holds the most, with 50.
Standing records at Portland by the year they were set
Year set
Standing records
1874
19
1875
27
1876
36
1877
22
1878
29
1879
22
1880
25
1881
33
1882
18
1883
16
1884
17
1885
11
1886
27
1887
30
1888
50
1889
17
1890
23
1891
31
1892
26
1893
16
1894
31
1895
29
1896
29
1897
18
1898
9
1899
22
1900
27
1901
18
1902
19
1903
23
1904
22
1905
18
1906
23
1907
33
1908
21
1909
23
1910
13
1911
23
1912
22
1913
21
1914
46
1915
16
1916
21
1917
30
1918
28
1919
20
1920
20
1921
20
1922
15
1923
27
1924
15
1925
11
1926
7
1927
19
1928
15
1929
21
1930
22
1931
19
1932
20
1933
17
1934
28
1935
12
1936
17
1937
18
1938
26
1939
7
1940
8
All-Time Record Progression
10 new records
10 all-time records were set at Portland between 24 January 1907 and 16 January 1923. Each dot is a new record.
When Portland set new all-time records
Date
Kind
Detail
1907-01-24
Record low minimum temperature
Record low minimum temperature -26.7 C (-16.1 F)
1908-07-12
Record high maximum temperature
Record high maximum temperature 36.7 C (98.1 F)
1911-07-04
Record high maximum temperature
Record high maximum temperature 39.4 C (102.9 F)
1911-07-04
Record high minimum temperature
Record high minimum temperature 26.1 C (79.0 F)
1914-02-12
Record low minimum temperature
Record low minimum temperature -27.2 C (-17.0 F)
1917-12-29
Record low maximum temperature
Record low maximum temperature -19.4 C (-2.9 F)
1917-12-30
Record low minimum temperature
Record low minimum temperature -29.4 C (-20.9 F)
1918-02-05
Record low maximum temperature
Record low maximum temperature -20.0 C (-4.0 F)
1923-01-15
Record snow depth
Record snow depth 132.1 cm (52.0 in)
1923-01-16
Record snow depth
Record snow depth 139.7 cm (55.0 in)
Wettest Day of Each Month
Sep: 134.1 mm (5.3 in)
The wettest day on record for each calendar month at Portland. The most was 134.1 mm (5.3 in) on 6 September 1896.
Record daily precipitation for each month at Portland
Month
Record daily precipitation (mm)
Date
Jan
75.7 mm (3.0 in)
15 January 1940
Feb
77.7 mm (3.1 in)
22 February 1898
Mar
83.8 mm (3.3 in)
16 March 1937
Apr
83.8 mm (3.3 in)
1 April 1922
May
121.4 mm (4.8 in)
17 May 1916
Jun
110.5 mm (4.4 in)
18 June 1922
Jul
108.0 mm (4.3 in)
28 July 1939
Aug
62.5 mm (2.5 in)
12 August 1892
Sep
134.1 mm (5.3 in)
6 September 1896
Oct
99.8 mm (3.9 in)
7 October 1873
Nov
84.6 mm (3.3 in)
28 November 1889
Dec
65.5 mm (2.6 in)
10 December 1878
Period of Record Coverage
1874 to 1940
Complete yearUnder 90 percent of days
67 years of record at Portland, 1874 to 1940. 2 years have data for under 90 percent of days and are left out of rankings: 1874, 1940.
Cooler than the station meanWarmer than the station mean
One stripe for each of 65 complete years at Portland, 1875 to 1939. Blue stripes are years cooler than the station's own mean of 7.6 C (45.8 F); red stripes are warmer. The coolest year was 1904, at 5.6 C (42.1 F), and the warmest was 1878, at 9.7 C (49.5 F). The strongest colour marks a difference of 2.1 C (3.8 F).
Annual mean temperature at Portland as warming stripes, 1875 to 1939
Year
Annual mean temperature
Difference from the station mean
1875
6.8 C
-0.85 C
1876
8.1 C
+0.48 C
1877
9.3 C
+1.68 C
1878
9.7 C
+2.10 C
1879
8.5 C
+0.86 C
1880
9.2 C
+1.54 C
1881
9.0 C
+1.40 C
1882
8.9 C
+1.24 C
1883
7.9 C
+0.28 C
1884
8.7 C
+1.09 C
1885
7.5 C
-0.10 C
1886
6.9 C
-0.78 C
1887
6.8 C
-0.85 C
1888
6.0 C
-1.64 C
1889
8.1 C
+0.45 C
1890
6.8 C
-0.81 C
1891
7.7 C
+0.03 C
1892
7.3 C
-0.35 C
1893
6.3 C
-1.34 C
1894
7.5 C
-0.16 C
1895
7.3 C
-0.31 C
1896
7.0 C
-0.61 C
1897
7.3 C
-0.38 C
1898
8.0 C
+0.31 C
1899
7.6 C
-0.04 C
1900
7.9 C
+0.21 C
1901
7.3 C
-0.30 C
1902
7.4 C
-0.21 C
1903
7.2 C
-0.41 C
1904
5.6 C
-2.02 C
1905
6.7 C
-0.99 C
1906
7.2 C
-0.45 C
1907
6.3 C
-1.35 C
1908
7.8 C
+0.16 C
1909
7.5 C
-0.13 C
1910
7.7 C
+0.03 C
1911
7.5 C
-0.15 C
1912
7.2 C
-0.42 C
1913
8.3 C
+0.63 C
1914
6.7 C
-0.90 C
1915
7.9 C
+0.29 C
1916
6.9 C
-0.70 C
1917
5.9 C
-1.76 C
1918
6.8 C
-0.88 C
1919
7.7 C
+0.09 C
1920
7.4 C
-0.28 C
1921
8.4 C
+0.78 C
1922
7.7 C
+0.06 C
1923
7.2 C
-0.45 C
1924
7.3 C
-0.32 C
1925
7.7 C
+0.09 C
1926
6.6 C
-1.05 C
1927
8.1 C
+0.44 C
1928
7.9 C
+0.24 C
1929
7.8 C
+0.17 C
1930
8.5 C
+0.86 C
1931
9.3 C
+1.61 C
1932
8.9 C
+1.28 C
1933
8.1 C
+0.48 C
1934
7.5 C
-0.18 C
1935
7.7 C
+0.09 C
1936
7.9 C
+0.22 C
1937
9.0 C
+1.31 C
1938
8.6 C
+0.99 C
1939
7.5 C
-0.14 C
The fitted trend in annual mean temperature here over 1875 to 1939 is 0.00 C (-0.12 to 0.11) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: -0.01 F (-0.21 to 0.20) 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 Portland
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.00 C (-0.12 to 0.11) per decade
-0.01 F (-0.21 to 0.20) per decade
1875 to 1939
65
Not clearly different from zero
Mean daily maximum
-0.02 C (-0.13 to 0.10) per decade
-0.03 F (-0.24 to 0.18) per decade
1875 to 1939
65
Not clearly different from zero
Mean daily minimum
0.01 C (-0.11 to 0.12) per decade
0.01 F (-0.20 to 0.22) per decade
1875 to 1939
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
1871 to 1940
Yearly extremes at Portland: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
39.4 C (102.9 F)
1911
34.4 C (93.9 F)
67
Coldest night (TNn)
-29.4 C (-20.9 F)
1917
-21.7 C (-7.1 F)
67
Wettest day (Rx1day)
134.1 mm (5.3 in)
1896
63.0 mm (2.5 in)
70
Wettest five days (Rx5day)
225.8 mm (8.9 in)
1922
92.2 mm (3.6 in)
70
Longest dry spell (CDD)
35 days
1924
17 days
70
Hottest day (TXx)
The hottest day of the year at Portland, 1871 to 1940. The record is 39.4 C (102.9 F) in 1911, marked on the chart; the median year is 34.4 C (93.9 F).
Hottest day (TXx) at Portland by year
Year
Hottest day (TXx)
1871
n/a
1872
n/a
1873
n/a
1874
33.3 C (91.9 F)
1875
32.8 C (91.0 F)
1876
36.1 C (97.0 F)
1877
32.2 C (90.0 F)
1878
35.6 C (96.1 F)
1879
33.9 C (93.0 F)
1880
34.4 C (93.9 F)
1881
34.4 C (93.9 F)
1882
34.4 C (93.9 F)
1883
31.7 C (89.1 F)
1884
31.7 C (89.1 F)
1885
32.2 C (90.0 F)
1886
34.4 C (93.9 F)
1887
35.6 C (96.1 F)
1888
35.6 C (96.1 F)
1889
33.3 C (91.9 F)
1890
33.9 C (93.0 F)
1891
35.0 C (95.0 F)
1892
35.0 C (95.0 F)
1893
33.9 C (93.0 F)
1894
36.1 C (97.0 F)
1895
33.9 C (93.0 F)
1896
33.3 C (91.9 F)
1897
34.4 C (93.9 F)
1898
36.1 C (97.0 F)
1899
33.9 C (93.0 F)
1900
34.4 C (93.9 F)
1901
35.6 C (96.1 F)
1902
32.2 C (90.0 F)
1903
32.8 C (91.0 F)
1904
33.3 C (91.9 F)
1905
32.8 C (91.0 F)
1906
33.9 C (93.0 F)
1907
35.0 C (95.0 F)
1908
36.7 C (98.1 F)
1909
34.4 C (93.9 F)
1910
32.8 C (91.0 F)
1911
39.4 C (102.9 F)
1912
33.3 C (91.9 F)
1913
38.3 C (100.9 F)
1914
33.3 C (91.9 F)
1915
31.7 C (89.1 F)
1916
34.4 C (93.9 F)
1917
33.3 C (91.9 F)
1918
34.4 C (93.9 F)
1919
36.7 C (98.1 F)
1920
33.3 C (91.9 F)
1921
33.9 C (93.0 F)
1922
34.4 C (93.9 F)
1923
35.6 C (96.1 F)
1924
32.8 C (91.0 F)
1925
35.0 C (95.0 F)
1926
37.8 C (100.0 F)
1927
32.8 C (91.0 F)
1928
35.0 C (95.0 F)
1929
35.6 C (96.1 F)
1930
33.3 C (91.9 F)
1931
36.7 C (98.1 F)
1932
31.7 C (89.1 F)
1933
33.9 C (93.0 F)
1934
35.6 C (96.1 F)
1935
35.0 C (95.0 F)
1936
35.6 C (96.1 F)
1937
36.7 C (98.1 F)
1938
33.3 C (91.9 F)
1939
35.6 C (96.1 F)
1940
35.0 C (95.0 F)
Coldest night (TNn)
The coldest night of the year at Portland, 1871 to 1940. The record is -29.4 C (-20.9 F) in 1917, marked on the chart; the median year is -21.7 C (-7.1 F).
Coldest night (TNn) at Portland by year
Year
Coldest night (TNn)
1871
n/a
1872
n/a
1873
n/a
1874
-18.9 C (-2.0 F)
1875
-24.4 C (-11.9 F)
1876
-23.3 C (-9.9 F)
1877
-21.7 C (-7.1 F)
1878
-20.6 C (-5.1 F)
1879
-18.9 C (-2.0 F)
1880
-19.4 C (-2.9 F)
1881
-21.1 C (-6.0 F)
1882
-24.4 C (-11.9 F)
1883
-22.2 C (-8.0 F)
1884
-21.1 C (-6.0 F)
1885
-20.6 C (-5.1 F)
1886
-24.4 C (-11.9 F)
1887
-26.1 C (-15.0 F)
1888
-24.4 C (-11.9 F)
1889
-22.2 C (-8.0 F)
1890
-20.0 C (-4.0 F)
1891
-20.0 C (-4.0 F)
1892
-20.6 C (-5.1 F)
1893
-22.8 C (-9.0 F)
1894
-26.1 C (-15.0 F)
1895
-23.9 C (-11.0 F)
1896
-25.0 C (-13.0 F)
1897
-22.2 C (-8.0 F)
1898
-21.1 C (-6.0 F)
1899
-23.3 C (-9.9 F)
1900
-22.2 C (-8.0 F)
1901
-23.9 C (-11.0 F)
1902
-25.6 C (-14.1 F)
1903
-22.8 C (-9.0 F)
1904
-23.3 C (-9.9 F)
1905
-23.3 C (-9.9 F)
1906
-20.6 C (-5.1 F)
1907
-26.7 C (-16.1 F)
1908
-20.6 C (-5.1 F)
1909
-20.0 C (-4.0 F)
1910
-20.0 C (-4.0 F)
1911
-17.8 C (0.0 F)
1912
-21.7 C (-7.1 F)
1913
-18.9 C (-2.0 F)
1914
-27.2 C (-17.0 F)
1915
-20.6 C (-5.1 F)
1916
-20.6 C (-5.1 F)
1917
-29.4 C (-20.9 F)
1918
-25.6 C (-14.1 F)
1919
-23.3 C (-9.9 F)
1920
-26.7 C (-16.1 F)
1921
-19.4 C (-2.9 F)
1922
-22.2 C (-8.0 F)
1923
-22.2 C (-8.0 F)
1924
-27.8 C (-18.0 F)
1925
-21.7 C (-7.1 F)
1926
-17.8 C (0.0 F)
1927
-21.7 C (-7.1 F)
1928
-20.6 C (-5.1 F)
1929
-17.2 C (1.0 F)
1930
-20.6 C (-5.1 F)
1931
-17.2 C (1.0 F)
1932
-17.8 C (0.0 F)
1933
-27.8 C (-18.0 F)
1934
-27.8 C (-18.0 F)
1935
-23.9 C (-11.0 F)
1936
-18.3 C (-0.9 F)
1937
-15.0 C (5.0 F)
1938
-18.3 C (-0.9 F)
1939
-18.3 C (-0.9 F)
1940
-18.3 C (-0.9 F)
Wettest day (Rx1day)
The wettest day of the year at Portland, 1871 to 1940. The record is 134.1 mm (5.3 in) in 1896, marked on the chart; the median year is 63.0 mm (2.5 in).
Wettest day (Rx1day) at Portland by year
Year
Wettest day (Rx1day)
1871
68.1 mm (2.7 in)
1872
53.3 mm (2.1 in)
1873
99.8 mm (3.9 in)
1874
54.9 mm (2.2 in)
1875
63.5 mm (2.5 in)
1876
38.1 mm (1.5 in)
1877
80.3 mm (3.2 in)
1878
65.5 mm (2.6 in)
1879
51.1 mm (2.0 in)
1880
63.8 mm (2.5 in)
1881
61.2 mm (2.4 in)
1882
67.6 mm (2.7 in)
1883
52.1 mm (2.1 in)
1884
65.0 mm (2.6 in)
1885
74.9 mm (2.9 in)
1886
62.0 mm (2.4 in)
1887
55.1 mm (2.2 in)
1888
52.1 mm (2.1 in)
1889
84.6 mm (3.3 in)
1890
58.9 mm (2.3 in)
1891
53.3 mm (2.1 in)
1892
62.5 mm (2.5 in)
1893
67.6 mm (2.7 in)
1894
69.6 mm (2.7 in)
1895
56.4 mm (2.2 in)
1896
134.1 mm (5.3 in)
1897
52.3 mm (2.1 in)
1898
77.7 mm (3.1 in)
1899
53.3 mm (2.1 in)
1900
76.5 mm (3.0 in)
1901
71.9 mm (2.8 in)
1902
55.9 mm (2.2 in)
1903
61.0 mm (2.4 in)
1904
58.9 mm (2.3 in)
1905
59.2 mm (2.3 in)
1906
73.2 mm (2.9 in)
1907
84.6 mm (3.3 in)
1908
35.6 mm (1.4 in)
1909
38.1 mm (1.5 in)
1910
30.0 mm (1.2 in)
1911
70.9 mm (2.8 in)
1912
64.5 mm (2.5 in)
1913
42.9 mm (1.7 in)
1914
57.7 mm (2.3 in)
1915
93.0 mm (3.7 in)
1916
121.4 mm (4.8 in)
1917
105.2 mm (4.1 in)
1918
52.6 mm (2.1 in)
1919
52.3 mm (2.1 in)
1920
71.6 mm (2.8 in)
1921
38.9 mm (1.5 in)
1922
110.5 mm (4.4 in)
1923
44.2 mm (1.7 in)
1924
64.0 mm (2.5 in)
1925
50.5 mm (2.0 in)
1926
68.6 mm (2.7 in)
1927
54.9 mm (2.2 in)
1928
58.7 mm (2.3 in)
1929
66.3 mm (2.6 in)
1930
68.6 mm (2.7 in)
1931
67.6 mm (2.7 in)
1932
100.6 mm (4.0 in)
1933
58.9 mm (2.3 in)
1934
63.8 mm (2.5 in)
1935
57.2 mm (2.3 in)
1936
56.9 mm (2.2 in)
1937
83.8 mm (3.3 in)
1938
49.0 mm (1.9 in)
1939
108.0 mm (4.3 in)
1940
75.7 mm (3.0 in)
Wettest five days (Rx5day)
The wettest five days of the year at Portland, 1871 to 1940. The record is 225.8 mm (8.9 in) in 1922, marked on the chart; the median year is 92.2 mm (3.6 in).
Wettest five days (Rx5day) at Portland by year
Year
Wettest five days (Rx5day)
1871
141.2 mm (5.6 in)
1872
87.6 mm (3.4 in)
1873
109.7 mm (4.3 in)
1874
71.7 mm (2.8 in)
1875
68.6 mm (2.7 in)
1876
69.9 mm (2.8 in)
1877
131.1 mm (5.2 in)
1878
84.6 mm (3.3 in)
1879
83.6 mm (3.3 in)
1880
78.8 mm (3.1 in)
1881
76.2 mm (3.0 in)
1882
133.4 mm (5.3 in)
1883
79.5 mm (3.1 in)
1884
125.8 mm (5.0 in)
1885
80.0 mm (3.1 in)
1886
151.0 mm (5.9 in)
1887
88.9 mm (3.5 in)
1888
103.8 mm (4.1 in)
1889
86.4 mm (3.4 in)
1890
98.0 mm (3.9 in)
1891
92.7 mm (3.6 in)
1892
106.7 mm (4.2 in)
1893
126.8 mm (5.0 in)
1894
100.1 mm (3.9 in)
1895
84.1 mm (3.3 in)
1896
173.7 mm (6.8 in)
1897
64.2 mm (2.5 in)
1898
115.1 mm (4.5 in)
1899
66.2 mm (2.6 in)
1900
115.1 mm (4.5 in)
1901
108.4 mm (4.3 in)
1902
82.0 mm (3.2 in)
1903
92.2 mm (3.6 in)
1904
99.5 mm (3.9 in)
1905
83.8 mm (3.3 in)
1906
92.0 mm (3.6 in)
1907
102.6 mm (4.0 in)
1908
63.9 mm (2.5 in)
1909
81.4 mm (3.2 in)
1910
60.2 mm (2.4 in)
1911
81.6 mm (3.2 in)
1912
107.2 mm (4.2 in)
1913
60.1 mm (2.4 in)
1914
61.2 mm (2.4 in)
1915
116.9 mm (4.6 in)
1916
125.2 mm (4.9 in)
1917
117.4 mm (4.6 in)
1918
72.7 mm (2.9 in)
1919
63.0 mm (2.5 in)
1920
93.2 mm (3.7 in)
1921
92.2 mm (3.6 in)
1922
225.8 mm (8.9 in)
1923
81.3 mm (3.2 in)
1924
68.9 mm (2.7 in)
1925
107.1 mm (4.2 in)
1926
74.0 mm (2.9 in)
1927
66.0 mm (2.6 in)
1928
98.6 mm (3.9 in)
1929
90.6 mm (3.6 in)
1930
97.3 mm (3.8 in)
1931
94.6 mm (3.7 in)
1932
109.2 mm (4.3 in)
1933
114.8 mm (4.5 in)
1934
99.4 mm (3.9 in)
1935
111.6 mm (4.4 in)
1936
69.3 mm (2.7 in)
1937
99.5 mm (3.9 in)
1938
77.9 mm (3.1 in)
1939
119.9 mm (4.7 in)
1940
88.8 mm (3.5 in)
Longest dry spell (CDD)
The longest dry spell of the year at Portland, 1871 to 1940. The record is 35 days in 1924, marked on the chart; the median year is 17 days.
Longest dry spell (CDD) at Portland by year
Year
Longest dry spell (CDD)
1871
20 days
1872
24 days
1873
19 days
1874
18 days
1875
17 days
1876
15 days
1877
22 days
1878
14 days
1879
17 days
1880
18 days
1881
12 days
1882
20 days
1883
16 days
1884
14 days
1885
13 days
1886
30 days
1887
19 days
1888
14 days
1889
23 days
1890
17 days
1891
14 days
1892
16 days
1893
11 days
1894
17 days
1895
15 days
1896
13 days
1897
19 days
1898
17 days
1899
10 days
1900
19 days
1901
18 days
1902
14 days
1903
23 days
1904
17 days
1905
23 days
1906
15 days
1907
13 days
1908
28 days
1909
13 days
1910
16 days
1911
19 days
1912
27 days
1913
18 days
1914
21 days
1915
18 days
1916
12 days
1917
22 days
1918
25 days
1919
17 days
1920
26 days
1921
23 days
1922
19 days
1923
18 days
1924
35 days
1925
20 days
1926
13 days
1927
16 days
1928
13 days
1929
14 days
1930
13 days
1931
17 days
1932
15 days
1933
13 days
1934
20 days
1935
14 days
1936
15 days
1937
10 days
1938
15 days
1939
24 days
1940
19 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 Portland falls on 21 April and the median first autumn frost on 24 October, which leaves a median of 186 days between them.
In 1910 to 1939 the median growing season was 186 days. That is 1 day fewer than in 1875 to 1904.
Fitted over all years, the growing season changes by -0.6 days per decade at this station.
Frost dates and growing season at Portland
Measure
Median, all years
Earliest period (1875 to 1904)
Recent period (1910 to 1939)
Recent against earliest
Fitted trend
Last spring frost
21 April
20 April
24 April
4 days later
+1.1 days per decade
First autumn frost
24 October
21 October
27 October
6 days later
+0.5 days per decade
Growing days
186 days
187 days
186 days
1 day fewer
-0.6 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
64 years, 1872 to 1940
A day with at least 62.2 mm (2.4 in) of rain is expected about once in 2 years. A day with at least 135.9 mm (5.4 in) of rain is expected about once in 100 years.
Rainfall return levels at Portland: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
62.2 mm (2.4 in)
5 years
79.5 mm (3.1 in)
10 years
91.9 mm (3.6 in)
25 years
108.7 mm (4.3 in)
50 years
122.0 mm (4.8 in)
100 years
135.9 mm (5.4 in)
Longer than the 64 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, 64 years of values from 1872 to 1940.
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: 134.1 mm (5.3 in) in 1896; 121.4 mm (4.8 in) in 1916; 110.5 mm (4.4 in) in 1922.
Station Changes
1 suspected
One change was suspected in the annual mean temperature of Portland, at 1923. Each is measured against neighbouring stations.
Relative to 5 neighbouring stations, the station's annual mean temperature from 1923 ran 0.2 C (0.4 F) higher than in the years before (likely change).
Suspected changes in the annual mean temperature at Portland, against neighbouring stations
Year
Shift (C)
Shift (F)
Strength
Neighbours
1923
+0.2
+0.4
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 Portland standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Portland 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.