Record envelope, standing records and threshold days for Mason City 4SE (USC00115413), Illinois, United States, with 77 years of record.
Key Facts for Mason City 4SE
Mason City 4SE (USC00115413) is a weather station in Illinois, United States at 40.16 latitude and -89.65 longitude, 183 m (600 ft) above sea level.
The station reports from 1937 to 2013, 77 years of record.
1,464 records set at Mason City 4SE still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Mason City 4SE set a daily record precipitation of 28.7 mm (1.1 in) on 31 May 2013.
About the Station
Location: Illinois, United States, 40.16 latitude, -89.65 longitude.
Elevation: 183 m (600 ft).
Period of record: 1937 to 2013, 77 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 Mason City 4SE. 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 Mason City 4SE, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
21.1 C (70.0 F)
-31.1 C (-24.0 F)
n/a
n/a
Feb
23.9 C (75.0 F)
-27.2 C (-17.0 F)
n/a
n/a
Mar
30.6 C (87.1 F)
-22.2 C (-8.0 F)
n/a
n/a
Apr
32.8 C (91.0 F)
-9.4 C (15.1 F)
n/a
n/a
May
35.6 C (96.1 F)
-1.7 C (28.9 F)
n/a
n/a
Jun
39.4 C (102.9 F)
3.9 C (39.0 F)
n/a
n/a
Jul
40.0 C (104.0 F)
7.2 C (45.0 F)
n/a
n/a
Aug
39.4 C (102.9 F)
4.4 C (39.9 F)
n/a
n/a
Sep
37.2 C (99.0 F)
-2.2 C (28.0 F)
n/a
n/a
Oct
34.4 C (93.9 F)
-7.8 C (18.0 F)
n/a
n/a
Nov
27.8 C (82.0 F)
-20.6 C (-5.1 F)
n/a
n/a
Dec
22.8 C (73.0 F)
-30.6 C (-23.1 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Mason City 4SE still stand. 1983 holds the most, with 56.
Standing records at Mason City 4SE by the year they were set
Year set
Standing records
1962
27
1963
47
1964
39
1965
37
1966
16
1967
46
1968
25
1969
9
1970
34
1971
40
1972
33
1973
21
1974
35
1975
28
1976
42
1977
34
1978
29
1979
34
1980
25
1981
18
1982
48
1983
56
1984
42
1985
39
1986
33
1987
36
1988
33
1989
46
1990
40
1991
44
1992
38
1993
19
1994
17
1995
22
1996
37
1997
33
1998
21
1999
29
2000
38
2001
18
2002
21
2003
6
2004
10
2005
20
2006
24
2007
4
2008
22
2009
27
2010
13
2011
9
All-Time Record Progression
5 new records
5 all-time records were set at Mason City 4SE between 4 October 1991 and 2 February 2011. Each dot is a new record.
When Mason City 4SE set new all-time records
Date
Kind
Detail
1991-10-04
Record daily precipitation
Record daily precipitation 122.4 mm (4.8 in)
1993-09-14
Record daily precipitation
Record daily precipitation 123.7 mm (4.9 in)
2005-07-25
Record high maximum temperature
Record high maximum temperature 40.0 C (104.0 F)
2008-02-01
Record daily snowfall
Record daily snowfall 22.9 cm (9.0 in)
2011-02-02
Record daily snowfall
Record daily snowfall 25.4 cm (10.0 in)
Wettest Day of Each Month
Sep: 123.7 mm (4.9 in)
The wettest day on record for each calendar month at Mason City 4SE. The most was 123.7 mm (4.9 in) on 14 September 1993.
Record daily precipitation for each month at Mason City 4SE
Month
Record daily precipitation (mm)
Date
Jan
62.2 mm (2.4 in)
8 January 2008
Feb
52.8 mm (2.1 in)
22 February 1990
Mar
70.4 mm (2.8 in)
11 March 1939
Apr
70.1 mm (2.8 in)
30 April 1970
May
98.8 mm (3.9 in)
17 May 1995
Jun
93.5 mm (3.7 in)
27 June 1951
Jul
104.1 mm (4.1 in)
29 July 2002
Aug
82.8 mm (3.3 in)
6 August 1991
Sep
123.7 mm (4.9 in)
14 September 1993
Oct
122.4 mm (4.8 in)
4 October 1991
Nov
122.2 mm (4.8 in)
5 November 2004
Dec
78.7 mm (3.1 in)
3 December 1982
Period of Record Coverage
1962 to 2011
Complete yearUnder 90 percent of days
50 years of record at Mason City 4SE, 1962 to 2011. 14 years have data for under 90 percent of days and are left out of rankings: 1962, 1964, 1965, 1966, 1968, 1969, 2001, 2002 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 35 complete years at Mason City 4SE, 1963 to 2010. Blue stripes are years cooler than the station's own mean of 11.2 C (52.2 F); red stripes are warmer. The coolest year was 2008, at 9.9 C (49.7 F), and the warmest was 1998, at 13.1 C (55.6 F). The strongest colour marks a difference of 1.9 C (3.4 F).
Annual mean temperature at Mason City 4SE as warming stripes, 1963 to 2010
Year
Annual mean temperature
Difference from the station mean
1963
10.6 C
-0.60 C
1967
10.7 C
-0.58 C
1970
11.2 C
-0.06 C
1971
11.7 C
+0.50 C
1972
10.5 C
-0.71 C
1973
12.0 C
+0.72 C
1974
11.2 C
0.00 C
1976
10.5 C
-0.71 C
1977
11.1 C
-0.13 C
1978
10.0 C
-1.23 C
1979
10.0 C
-1.26 C
1980
11.1 C
-0.12 C
1981
11.3 C
+0.09 C
1982
10.7 C
-0.52 C
1983
11.6 C
+0.36 C
1984
11.5 C
+0.29 C
1985
10.9 C
-0.35 C
1986
11.7 C
+0.46 C
1987
12.8 C
+1.60 C
1988
11.8 C
+0.53 C
1989
10.6 C
-0.65 C
1990
12.5 C
+1.30 C
1991
12.4 C
+1.14 C
1992
11.4 C
+0.20 C
1993
10.9 C
-0.38 C
1994
11.5 C
+0.23 C
1995
11.2 C
-0.01 C
1996
10.5 C
-0.72 C
1997
10.9 C
-0.32 C
1998
13.1 C
+1.90 C
1999
12.2 C
+0.95 C
2000
11.9 C
+0.68 C
2008
9.9 C
-1.37 C
2009
10.3 C
-0.90 C
2010
11.0 C
-0.25 C
The fitted trend in annual mean temperature here over 1963 to 2010 is 0.1 C (-0.2 to 0.3) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: 0.1 F (-0.3 to 0.6) per decade. The slope is a straight line fitted to 35 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Mason City 4SE
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.1 C (-0.2 to 0.3) per decade
0.1 F (-0.3 to 0.6) per decade
1963 to 2010
35
Not clearly different from zero
Mean daily maximum
0.05 C (-0.21 to 0.30) per decade
0.1 F (-0.4 to 0.5) per decade
1963 to 2010
35
Not clearly different from zero
Mean daily minimum
0.1 C (-0.1 to 0.4) per decade
0.2 F (-0.3 to 0.6) per decade
1963 to 2010
35
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
1937 to 2013
Yearly extremes at Mason City 4SE: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
40.0 C (104.0 F)
2005
36.1 C (97.0 F)
50
Coldest night (TNn)
-31.1 C (-24.0 F)
1977
-23.3 C (-9.9 F)
50
Wettest day (Rx1day)
123.7 mm (4.9 in)
1993
60.7 mm (2.4 in)
59
Wettest five days (Rx5day)
185.9 mm (7.3 in)
1969
91.5 mm (3.6 in)
59
Longest dry spell (CDD)
39 days
1987
20 days
59
Hottest day (TXx)
The hottest day of the year at Mason City 4SE, 1937 to 2013. The record is 40.0 C (104.0 F) in 2005, marked on the chart; the median year is 36.1 C (97.0 F).
Hottest day (TXx) at Mason City 4SE by year
Year
Hottest day (TXx)
1937
n/a
1938
n/a
1939
n/a
1948
n/a
1949
n/a
1950
n/a
1951
n/a
1962
37.2 C (99.0 F)
1963
36.1 C (97.0 F)
1964
38.9 C (102.0 F)
1965
36.7 C (98.1 F)
1966
39.4 C (102.9 F)
1967
35.6 C (96.1 F)
1968
36.1 C (97.0 F)
1969
33.9 C (93.0 F)
1970
36.7 C (98.1 F)
1971
37.2 C (99.0 F)
1972
35.0 C (95.0 F)
1973
33.9 C (93.0 F)
1974
37.2 C (99.0 F)
1975
32.8 C (91.0 F)
1976
37.2 C (99.0 F)
1977
36.7 C (98.1 F)
1978
35.6 C (96.1 F)
1979
35.0 C (95.0 F)
1980
37.2 C (99.0 F)
1981
34.4 C (93.9 F)
1982
34.4 C (93.9 F)
1983
39.4 C (102.9 F)
1984
37.2 C (99.0 F)
1985
35.0 C (95.0 F)
1986
33.9 C (93.0 F)
1987
39.4 C (102.9 F)
1988
39.4 C (102.9 F)
1989
36.7 C (98.1 F)
1990
37.2 C (99.0 F)
1991
37.2 C (99.0 F)
1992
34.4 C (93.9 F)
1993
35.0 C (95.0 F)
1994
35.0 C (95.0 F)
1995
37.8 C (100.0 F)
1996
35.0 C (95.0 F)
1997
36.7 C (98.1 F)
1998
35.6 C (96.1 F)
1999
36.1 C (97.0 F)
2000
36.7 C (98.1 F)
2001
36.7 C (98.1 F)
2002
36.7 C (98.1 F)
2003
36.7 C (98.1 F)
2004
34.4 C (93.9 F)
2005
40.0 C (104.0 F)
2006
36.1 C (97.0 F)
2007
21.7 C (71.1 F)
2008
34.4 C (93.9 F)
2009
35.6 C (96.1 F)
2010
35.0 C (95.0 F)
2011
34.4 C (93.9 F)
2012
n/a
2013
n/a
Coldest night (TNn)
The coldest night of the year at Mason City 4SE, 1937 to 2013. The record is -31.1 C (-24.0 F) in 1977, marked on the chart; the median year is -23.3 C (-9.9 F).
Coldest night (TNn) at Mason City 4SE by year
Year
Coldest night (TNn)
1937
n/a
1938
n/a
1939
n/a
1948
n/a
1949
n/a
1950
n/a
1951
n/a
1962
-23.9 C (-11.0 F)
1963
-28.3 C (-18.9 F)
1964
-20.6 C (-5.1 F)
1965
-23.3 C (-9.9 F)
1966
-16.7 C (1.9 F)
1967
-22.2 C (-8.0 F)
1968
-26.1 C (-15.0 F)
1969
-16.7 C (1.9 F)
1970
-26.1 C (-15.0 F)
1971
-20.6 C (-5.1 F)
1972
-27.8 C (-18.0 F)
1973
-24.4 C (-11.9 F)
1974
-28.3 C (-18.9 F)
1975
-23.9 C (-11.0 F)
1976
-22.8 C (-9.0 F)
1977
-31.1 C (-24.0 F)
1978
-23.3 C (-9.9 F)
1979
-28.9 C (-20.0 F)
1980
-23.3 C (-9.9 F)
1981
-25.6 C (-14.1 F)
1982
-28.9 C (-20.0 F)
1983
-27.8 C (-18.0 F)
1984
-27.2 C (-17.0 F)
1985
-30.0 C (-22.0 F)
1986
-21.7 C (-7.1 F)
1987
-23.9 C (-11.0 F)
1988
-25.0 C (-13.0 F)
1989
-30.6 C (-23.1 F)
1990
-18.9 C (-2.0 F)
1991
-18.3 C (-0.9 F)
1992
-21.7 C (-7.1 F)
1993
-22.2 C (-8.0 F)
1994
-27.8 C (-18.0 F)
1995
-20.0 C (-4.0 F)
1996
-26.1 C (-15.0 F)
1997
-25.6 C (-14.1 F)
1998
-22.2 C (-8.0 F)
1999
-29.4 C (-20.9 F)
2000
-23.3 C (-9.9 F)
2001
-20.0 C (-4.0 F)
2002
-20.0 C (-4.0 F)
2003
-22.8 C (-9.0 F)
2004
-20.6 C (-5.1 F)
2005
-18.9 C (-2.0 F)
2006
-18.3 C (-0.9 F)
2007
-13.3 C (8.1 F)
2008
-20.6 C (-5.1 F)
2009
-26.7 C (-16.1 F)
2010
-23.3 C (-9.9 F)
2011
-21.7 C (-7.1 F)
2012
n/a
2013
n/a
Wettest day (Rx1day)
The wettest day of the year at Mason City 4SE, 1937 to 2013. The record is 123.7 mm (4.9 in) in 1993, marked on the chart; the median year is 60.7 mm (2.4 in).
Wettest day (Rx1day) at Mason City 4SE by year
Year
Wettest day (Rx1day)
1937
78.2 mm (3.1 in)
1938
54.4 mm (2.1 in)
1939
70.4 mm (2.8 in)
1948
88.4 mm (3.5 in)
1949
62.7 mm (2.5 in)
1950
45.2 mm (1.8 in)
1951
93.5 mm (3.7 in)
1962
73.7 mm (2.9 in)
1963
38.1 mm (1.5 in)
1964
57.2 mm (2.3 in)
1965
53.3 mm (2.1 in)
1966
50.8 mm (2.0 in)
1967
76.2 mm (3.0 in)
1968
43.2 mm (1.7 in)
1969
72.6 mm (2.9 in)
1970
70.1 mm (2.8 in)
1971
43.9 mm (1.7 in)
1972
56.4 mm (2.2 in)
1973
73.2 mm (2.9 in)
1974
82.6 mm (3.3 in)
1975
39.1 mm (1.5 in)
1976
51.1 mm (2.0 in)
1977
56.9 mm (2.2 in)
1978
44.7 mm (1.8 in)
1979
60.7 mm (2.4 in)
1980
53.3 mm (2.1 in)
1981
90.4 mm (3.6 in)
1982
78.7 mm (3.1 in)
1983
39.9 mm (1.6 in)
1984
81.3 mm (3.2 in)
1985
51.1 mm (2.0 in)
1986
59.2 mm (2.3 in)
1987
30.7 mm (1.2 in)
1988
78.7 mm (3.1 in)
1989
45.2 mm (1.8 in)
1990
84.6 mm (3.3 in)
1991
122.4 mm (4.8 in)
1992
69.3 mm (2.7 in)
1993
123.7 mm (4.9 in)
1994
38.6 mm (1.5 in)
1995
98.8 mm (3.9 in)
1996
32.0 mm (1.3 in)
1997
53.1 mm (2.1 in)
1998
68.3 mm (2.7 in)
1999
40.1 mm (1.6 in)
2000
86.1 mm (3.4 in)
2001
50.8 mm (2.0 in)
2002
104.1 mm (4.1 in)
2003
106.7 mm (4.2 in)
2004
122.2 mm (4.8 in)
2005
21.1 mm (0.8 in)
2006
49.5 mm (1.9 in)
2007
40.6 mm (1.6 in)
2008
81.5 mm (3.2 in)
2009
66.5 mm (2.6 in)
2010
68.8 mm (2.7 in)
2011
39.9 mm (1.6 in)
2012
45.2 mm (1.8 in)
2013
76.2 mm (3.0 in)
Wettest five days (Rx5day)
The wettest five days of the year at Mason City 4SE, 1937 to 2013. The record is 185.9 mm (7.3 in) in 1969, marked on the chart; the median year is 91.5 mm (3.6 in).
Wettest five days (Rx5day) at Mason City 4SE by year
Year
Wettest five days (Rx5day)
1937
113.9 mm (4.5 in)
1938
84.9 mm (3.3 in)
1939
91.5 mm (3.6 in)
1948
127.5 mm (5.0 in)
1949
111.0 mm (4.4 in)
1950
95.6 mm (3.8 in)
1951
127.7 mm (5.0 in)
1962
115.4 mm (4.5 in)
1963
54.1 mm (2.1 in)
1964
86.7 mm (3.4 in)
1965
106.4 mm (4.2 in)
1966
85.6 mm (3.4 in)
1967
91.9 mm (3.6 in)
1968
65.8 mm (2.6 in)
1969
185.9 mm (7.3 in)
1970
107.7 mm (4.2 in)
1971
56.4 mm (2.2 in)
1972
106.9 mm (4.2 in)
1973
76.8 mm (3.0 in)
1974
93.3 mm (3.7 in)
1975
56.1 mm (2.2 in)
1976
61.0 mm (2.4 in)
1977
114.0 mm (4.5 in)
1978
73.0 mm (2.9 in)
1979
79.0 mm (3.1 in)
1980
93.9 mm (3.7 in)
1981
109.0 mm (4.3 in)
1982
134.9 mm (5.3 in)
1983
71.4 mm (2.8 in)
1984
93.0 mm (3.7 in)
1985
108.8 mm (4.3 in)
1986
94.0 mm (3.7 in)
1987
47.0 mm (1.9 in)
1988
102.8 mm (4.0 in)
1989
85.4 mm (3.4 in)
1990
90.2 mm (3.6 in)
1991
146.3 mm (5.8 in)
1992
130.0 mm (5.1 in)
1993
137.2 mm (5.4 in)
1994
72.1 mm (2.8 in)
1995
134.7 mm (5.3 in)
1996
66.5 mm (2.6 in)
1997
54.4 mm (2.1 in)
1998
77.2 mm (3.0 in)
1999
70.1 mm (2.8 in)
2000
86.1 mm (3.4 in)
2001
74.2 mm (2.9 in)
2002
111.0 mm (4.4 in)
2003
106.7 mm (4.2 in)
2004
122.2 mm (4.8 in)
2005
33.7 mm (1.3 in)
2006
59.6 mm (2.3 in)
2007
78.7 mm (3.1 in)
2008
159.9 mm (6.3 in)
2009
86.4 mm (3.4 in)
2010
91.4 mm (3.6 in)
2011
62.0 mm (2.4 in)
2012
68.8 mm (2.7 in)
2013
119.7 mm (4.7 in)
Longest dry spell (CDD)
The longest dry spell of the year at Mason City 4SE, 1937 to 2013. The record is 39 days in 1987, marked on the chart; the median year is 20 days.
Longest dry spell (CDD) at Mason City 4SE by year
Year
Longest dry spell (CDD)
1937
14 days
1938
24 days
1939
13 days
1948
15 days
1949
21 days
1950
30 days
1951
13 days
1962
16 days
1963
35 days
1964
35 days
1965
17 days
1966
19 days
1967
17 days
1968
21 days
1969
18 days
1970
16 days
1971
24 days
1972
18 days
1973
20 days
1974
17 days
1975
14 days
1976
25 days
1977
14 days
1978
21 days
1979
29 days
1980
17 days
1981
25 days
1982
17 days
1983
27 days
1984
16 days
1985
22 days
1986
31 days
1987
39 days
1988
22 days
1989
27 days
1990
16 days
1991
19 days
1992
18 days
1993
20 days
1994
16 days
1995
25 days
1996
27 days
1997
20 days
1998
19 days
1999
37 days
2000
16 days
2001
34 days
2002
26 days
2003
22 days
2004
27 days
2005
22 days
2006
16 days
2007
12 days
2008
24 days
2009
13 days
2010
27 days
2011
16 days
2012
21 days
2013
17 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
35 years with a frost
Across 35 years with a frost, the median last spring frost at Mason City 4SE falls on 21 April and the median first autumn frost on 11 October, which leaves a median of 174 days between them.
Fitted over all years, the growing season changes by +2.6 days per decade at this station.
Frost dates and growing season at Mason City 4SE
Measure
Median, all years
Earliest period
Recent period (1973 to 2010)
Recent against earliest
Fitted trend
Last spring frost
21 April
n/a
19 April
n/a
-2.9 days per decade
First autumn frost
11 October
n/a
11 October
n/a
-0.3 days per decade
Growing days
174 days
n/a
174 days
n/a
+2.6 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
40 years, 1938 to 2010
A day with at least 60.5 mm (2.4 in) of rain is expected about once in 2 years. A day with at least 132.9 mm (5.2 in) of rain is expected about once in 100 years.
Rainfall return levels at Mason City 4SE: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
60.5 mm (2.4 in)
5 years
80.5 mm (3.2 in)
10 years
93.5 mm (3.7 in)
25 years
109.6 mm (4.3 in)
50 years
121.4 mm (4.8 in)
Longer than the 40 years of record
100 years
132.9 mm (5.2 in)
Longer than the 40 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, 40 years of values from 1938 to 2010.
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: 123.7 mm (4.9 in) in 1993; 122.4 mm (4.8 in) in 1991; 98.8 mm (3.9 in) in 1995.
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Data for Mason City 4SE standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Mason City 4SE 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 2026-10-13 (13 October 2026). Records are computed by this site and are not official.