Record envelope, standing records and threshold days for Thermopolis 21WNW (USC00488888), Wyoming, United States, with 62 years of record.
Key Facts for Thermopolis 21WNW
Thermopolis 21WNW (USC00488888) is a weather station in Wyoming, United States at 43.72 latitude and -108.70 longitude, 1,679 m (5,510 ft) above sea level.
The station reports from 1951 to 2012, 62 years of record.
1,464 records set at Thermopolis 21WNW still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Thermopolis 21WNW set a daily record high minimum temperature of 3.3 C (37.9 F) on 31 March 2012.
About the Station
Location: Wyoming, United States, 43.72 latitude, -108.70 longitude.
Elevation: 1,679 m (5,510 ft).
Period of record: 1951 to 2012, 62 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 Thermopolis 21WNW. 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 Thermopolis 21WNW, 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)
-40.0 C (-40.0 F)
n/a
n/a
Feb
18.9 C (66.0 F)
-40.0 C (-40.0 F)
n/a
n/a
Mar
23.3 C (73.9 F)
-32.2 C (-26.0 F)
n/a
n/a
Apr
26.7 C (80.1 F)
-18.9 C (-2.0 F)
n/a
n/a
May
33.9 C (93.0 F)
-10.0 C (14.0 F)
n/a
n/a
Jun
36.1 C (97.0 F)
-5.6 C (21.9 F)
n/a
n/a
Jul
40.0 C (104.0 F)
-3.3 C (26.1 F)
n/a
n/a
Aug
36.7 C (98.1 F)
-3.3 C (26.1 F)
n/a
n/a
Sep
33.9 C (93.0 F)
-16.7 C (1.9 F)
n/a
n/a
Oct
31.1 C (88.0 F)
-20.6 C (-5.1 F)
n/a
n/a
Nov
21.7 C (71.1 F)
-32.2 C (-26.0 F)
n/a
n/a
Dec
20.6 C (69.1 F)
-40.0 C (-40.0 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Thermopolis 21WNW still stand. 1959 holds the most, with 51.
Standing records at Thermopolis 21WNW by the year they were set
Year set
Standing records
1957
6
1958
32
1959
51
1960
32
1961
22
1962
43
1963
37
1964
25
1965
41
1966
38
1967
23
1968
23
1969
27
1970
21
1971
12
1972
31
1973
20
1974
35
1975
27
1976
16
1977
20
1978
24
1979
12
1980
25
1981
14
1982
23
1983
5
1984
25
1985
40
1986
35
1987
22
1988
17
1989
39
1990
36
1991
18
1992
26
1993
41
1994
16
1995
24
1996
33
1997
18
1998
24
1999
16
2000
31
2001
44
2002
36
2003
43
2004
12
2005
21
2006
26
2007
38
2008
19
2009
34
2010
22
2011
13
2012
10
All-Time Record Progression
5 new records
5 all-time records were set at Thermopolis 21WNW between 20 December 1990 and 29 March 2007. Each dot is a new record.
When Thermopolis 21WNW set new all-time records
Date
Kind
Detail
1990-12-20
Record low maximum temperature
Record low maximum temperature -28.3 C (-18.9 F)
1990-12-21
Record low maximum temperature
Record low maximum temperature -29.4 C (-20.9 F)
1997-06-08
Record daily precipitation
Record daily precipitation 66.0 mm (2.6 in)
2003-08-13
Record high minimum temperature
Record high minimum temperature 23.3 C (73.9 F)
2007-03-29
Record snow depth
Record snow depth 38.1 cm (15.0 in)
Wettest Day of Each Month
Jun: 66.0 mm (2.6 in)
The wettest day on record for each calendar month at Thermopolis 21WNW. The most was 66.0 mm (2.6 in) on 8 June 1997.
Record daily precipitation for each month at Thermopolis 21WNW
Month
Record daily precipitation (mm)
Date
Jan
15.2 mm (0.6 in)
12 January 1972
Feb
14.7 mm (0.6 in)
28 February 2004
Mar
24.1 mm (0.9 in)
18 March 1992
Apr
52.6 mm (2.1 in)
27 April 1963
May
53.3 mm (2.1 in)
6 May 1993
Jun
66.0 mm (2.6 in)
8 June 1997
Jul
55.4 mm (2.2 in)
23 July 1983
Aug
46.0 mm (1.8 in)
30 August 1971
Sep
39.4 mm (1.6 in)
2 September 1973
Oct
50.8 mm (2.0 in)
30 October 2003
Nov
20.3 mm (0.8 in)
18 November 2001
Dec
17.8 mm (0.7 in)
5 December 1978
Period of Record Coverage
1957 to 2012
Complete yearUnder 90 percent of days
56 years of record at Thermopolis 21WNW, 1957 to 2012. 28 years have data for under 90 percent of days and are left out of rankings: 1957, 1971, 1972, 1973, 1975, 1976, 1977, 1978 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 35 complete years at Thermopolis 21WNW, 1958 to 2011. Blue stripes are years cooler than the station's own mean of 6.3 C (43.3 F); red stripes are warmer. The coolest year was 1993, at 3.8 C (38.8 F), and the warmest was 2006, at 8.1 C (46.5 F). The strongest colour marks a difference of 2.6 C (4.7 F).
Annual mean temperature at Thermopolis 21WNW as warming stripes, 1958 to 2011
Year
Annual mean temperature
Difference from the station mean
1958
6.8 C
+0.57 C
1959
6.0 C
-0.27 C
1960
6.4 C
+0.18 C
1961
6.1 C
-0.13 C
1962
6.2 C
-0.07 C
1963
6.7 C
+0.46 C
1964
5.6 C
-0.70 C
1965
5.8 C
-0.49 C
1966
6.9 C
+0.65 C
1967
6.1 C
-0.20 C
1968
5.7 C
-0.54 C
1969
6.6 C
+0.30 C
1970
5.8 C
-0.45 C
1971
5.2 C
-1.04 C
1973
5.8 C
-0.43 C
1974
6.3 C
+0.07 C
1975
4.5 C
-1.73 C
1976
5.8 C
-0.48 C
1977
6.6 C
+0.35 C
1980
6.9 C
+0.60 C
1987
6.3 C
+0.08 C
1988
6.5 C
+0.27 C
1990
5.4 C
-0.85 C
1991
5.4 C
-0.84 C
1993
3.8 C
-2.50 C
1995
6.6 C
+0.29 C
1998
6.6 C
+0.34 C
2001
7.8 C
+1.57 C
2002
6.6 C
+0.34 C
2003
7.2 C
+0.91 C
2005
7.4 C
+1.09 C
2006
8.1 C
+1.79 C
2008
6.3 C
+0.08 C
2010
7.0 C
+0.74 C
2011
6.4 C
+0.09 C
The fitted trend in annual mean temperature here over 1958 to 2011 is 0.15 C (-0.01 to 0.31) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: 0.27 F (-0.02 to 0.56) 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 Thermopolis 21WNW
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
0.15 C (-0.01 to 0.31) per decade
0.27 F (-0.02 to 0.56) per decade
1958 to 2011
35
Not clearly different from zero
Mean daily maximum
0.18 C (-0.01 to 0.38) per decade
0.33 F (-0.02 to 0.68) per decade
1958 to 2011
35
Not clearly different from zero
Mean daily minimum
0.12 C (-0.05 to 0.28) per decade
0.2 F (-0.1 to 0.5) per decade
1958 to 2011
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
1951 to 2012
Yearly extremes at Thermopolis 21WNW: 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)
1984
33.9 C (93.0 F)
56
Coldest night (TNn)
-40.0 C (-40.0 F)
1963
-30.3 C (-22.5 F)
56
Wettest day (Rx1day)
66.0 mm (2.6 in)
1997
28.1 mm (1.1 in)
58
Wettest five days (Rx5day)
87.6 mm (3.4 in)
2008
43.6 mm (1.7 in)
58
Longest dry spell (CDD)
69 days
1964
32 days
58
Hottest day (TXx)
The hottest day of the year at Thermopolis 21WNW, 1951 to 2012. The record is 40.0 C (104.0 F) in 1984, marked on the chart; the median year is 33.9 C (93.0 F).
Hottest day (TXx) at Thermopolis 21WNW by year
Year
Hottest day (TXx)
1951
n/a
1952
n/a
1957
34.4 C (93.9 F)
1958
33.9 C (93.0 F)
1959
35.6 C (96.1 F)
1960
36.1 C (97.0 F)
1961
35.0 C (95.0 F)
1962
31.7 C (89.1 F)
1963
31.7 C (89.1 F)
1964
33.9 C (93.0 F)
1965
32.8 C (91.0 F)
1966
33.3 C (91.9 F)
1967
31.7 C (89.1 F)
1968
32.2 C (90.0 F)
1969
33.9 C (93.0 F)
1970
33.9 C (93.0 F)
1971
32.8 C (91.0 F)
1972
32.2 C (90.0 F)
1973
35.0 C (95.0 F)
1974
33.3 C (91.9 F)
1975
33.9 C (93.0 F)
1976
33.3 C (91.9 F)
1977
33.9 C (93.0 F)
1978
32.8 C (91.0 F)
1979
34.4 C (93.9 F)
1980
32.8 C (91.0 F)
1981
32.2 C (90.0 F)
1982
33.3 C (91.9 F)
1983
32.8 C (91.0 F)
1984
40.0 C (104.0 F)
1985
35.0 C (95.0 F)
1986
33.9 C (93.0 F)
1987
30.6 C (87.1 F)
1988
35.6 C (96.1 F)
1989
36.1 C (97.0 F)
1990
33.9 C (93.0 F)
1991
31.7 C (89.1 F)
1992
30.6 C (87.1 F)
1993
33.3 C (91.9 F)
1994
33.3 C (91.9 F)
1995
34.4 C (93.9 F)
1996
33.3 C (91.9 F)
1997
32.2 C (90.0 F)
1998
36.1 C (97.0 F)
1999
34.4 C (93.9 F)
2000
35.6 C (96.1 F)
2001
36.7 C (98.1 F)
2002
37.8 C (100.0 F)
2003
37.2 C (99.0 F)
2004
34.4 C (93.9 F)
2005
35.6 C (96.1 F)
2006
37.8 C (100.0 F)
2007
37.2 C (99.0 F)
2008
33.9 C (93.0 F)
2009
35.0 C (95.0 F)
2010
35.0 C (95.0 F)
2011
33.3 C (91.9 F)
2012
22.8 C (73.0 F)
Coldest night (TNn)
The coldest night of the year at Thermopolis 21WNW, 1951 to 2012. The record is -40.0 C (-40.0 F) in 1963, marked on the chart; the median year is -30.3 C (-22.5 F).
Coldest night (TNn) at Thermopolis 21WNW by year
Year
Coldest night (TNn)
1951
n/a
1952
n/a
1957
-18.3 C (-0.9 F)
1958
-21.1 C (-6.0 F)
1959
-36.7 C (-34.1 F)
1960
-32.2 C (-26.0 F)
1961
-30.0 C (-22.0 F)
1962
-34.4 C (-29.9 F)
1963
-40.0 C (-40.0 F)
1964
-38.3 C (-36.9 F)
1965
-29.4 C (-20.9 F)
1966
-27.8 C (-18.0 F)
1967
-26.1 C (-15.0 F)
1968
-32.8 C (-27.0 F)
1969
-26.7 C (-16.1 F)
1970
-29.4 C (-20.9 F)
1971
-26.1 C (-15.0 F)
1972
-36.7 C (-34.1 F)
1973
-33.9 C (-29.0 F)
1974
-36.7 C (-34.1 F)
1975
-31.7 C (-25.1 F)
1976
-30.0 C (-22.0 F)
1977
-30.6 C (-23.1 F)
1978
-33.9 C (-29.0 F)
1979
-31.7 C (-25.1 F)
1980
-33.3 C (-27.9 F)
1981
-35.0 C (-31.0 F)
1982
-32.8 C (-27.0 F)
1983
-20.6 C (-5.1 F)
1984
-32.8 C (-27.0 F)
1985
-33.3 C (-27.9 F)
1986
-30.0 C (-22.0 F)
1987
-25.6 C (-14.1 F)
1988
-28.9 C (-20.0 F)
1989
-40.0 C (-40.0 F)
1990
-40.0 C (-40.0 F)
1991
-26.1 C (-15.0 F)
1992
-27.2 C (-17.0 F)
1993
-30.6 C (-23.1 F)
1994
-26.7 C (-16.1 F)
1995
-25.0 C (-13.0 F)
1996
-32.8 C (-27.0 F)
1997
-27.8 C (-18.0 F)
1998
-34.4 C (-29.9 F)
1999
-20.0 C (-4.0 F)
2000
-28.3 C (-18.9 F)
2001
-28.3 C (-18.9 F)
2002
-27.8 C (-18.0 F)
2003
-30.0 C (-22.0 F)
2004
-30.6 C (-23.1 F)
2005
-27.8 C (-18.0 F)
2006
-34.4 C (-29.9 F)
2007
-31.1 C (-24.0 F)
2008
-31.7 C (-25.1 F)
2009
-29.4 C (-20.9 F)
2010
-28.9 C (-20.0 F)
2011
-31.1 C (-24.0 F)
2012
-20.6 C (-5.1 F)
Wettest day (Rx1day)
The wettest day of the year at Thermopolis 21WNW, 1951 to 2012. The record is 66.0 mm (2.6 in) in 1997, marked on the chart; the median year is 28.1 mm (1.1 in).
Wettest day (Rx1day) at Thermopolis 21WNW by year
Year
Wettest day (Rx1day)
1951
23.4 mm (0.9 in)
1952
27.2 mm (1.1 in)
1957
12.7 mm (0.5 in)
1958
31.0 mm (1.2 in)
1959
19.1 mm (0.8 in)
1960
41.4 mm (1.6 in)
1961
32.8 mm (1.3 in)
1962
22.1 mm (0.9 in)
1963
52.6 mm (2.1 in)
1964
30.5 mm (1.2 in)
1965
33.0 mm (1.3 in)
1966
16.8 mm (0.7 in)
1967
33.5 mm (1.3 in)
1968
24.4 mm (1.0 in)
1969
28.7 mm (1.1 in)
1970
20.8 mm (0.8 in)
1971
46.0 mm (1.8 in)
1972
22.1 mm (0.9 in)
1973
39.4 mm (1.6 in)
1974
22.1 mm (0.9 in)
1975
37.8 mm (1.5 in)
1976
23.6 mm (0.9 in)
1977
24.9 mm (1.0 in)
1978
30.2 mm (1.2 in)
1979
34.5 mm (1.4 in)
1980
27.4 mm (1.1 in)
1981
29.2 mm (1.1 in)
1982
18.0 mm (0.7 in)
1983
55.4 mm (2.2 in)
1984
29.0 mm (1.1 in)
1985
26.9 mm (1.1 in)
1986
28.7 mm (1.1 in)
1987
27.4 mm (1.1 in)
1988
20.3 mm (0.8 in)
1989
21.3 mm (0.8 in)
1990
23.6 mm (0.9 in)
1991
26.7 mm (1.1 in)
1992
40.4 mm (1.6 in)
1993
53.3 mm (2.1 in)
1994
24.6 mm (1.0 in)
1995
34.3 mm (1.4 in)
1996
10.2 mm (0.4 in)
1997
66.0 mm (2.6 in)
1998
37.3 mm (1.5 in)
1999
40.6 mm (1.6 in)
2000
26.4 mm (1.0 in)
2001
34.0 mm (1.3 in)
2002
27.4 mm (1.1 in)
2003
50.8 mm (2.0 in)
2004
20.8 mm (0.8 in)
2005
43.7 mm (1.7 in)
2006
16.0 mm (0.6 in)
2007
18.5 mm (0.7 in)
2008
40.9 mm (1.6 in)
2009
23.4 mm (0.9 in)
2010
31.0 mm (1.2 in)
2011
40.6 mm (1.6 in)
2012
13.5 mm (0.5 in)
Wettest five days (Rx5day)
The wettest five days of the year at Thermopolis 21WNW, 1951 to 2012. The record is 87.6 mm (3.4 in) in 2008, marked on the chart; the median year is 43.6 mm (1.7 in).
Wettest five days (Rx5day) at Thermopolis 21WNW by year
Year
Wettest five days (Rx5day)
1951
39.9 mm (1.6 in)
1952
53.1 mm (2.1 in)
1957
12.7 mm (0.5 in)
1958
44.3 mm (1.7 in)
1959
29.7 mm (1.2 in)
1960
41.4 mm (1.6 in)
1961
46.8 mm (1.8 in)
1962
44.2 mm (1.7 in)
1963
74.7 mm (2.9 in)
1964
49.8 mm (2.0 in)
1965
48.5 mm (1.9 in)
1966
24.9 mm (1.0 in)
1967
65.8 mm (2.6 in)
1968
66.0 mm (2.6 in)
1969
42.5 mm (1.7 in)
1970
34.1 mm (1.3 in)
1971
66.3 mm (2.6 in)
1972
24.9 mm (1.0 in)
1973
65.6 mm (2.6 in)
1974
36.1 mm (1.4 in)
1975
76.4 mm (3.0 in)
1976
42.9 mm (1.7 in)
1977
38.8 mm (1.5 in)
1978
75.2 mm (3.0 in)
1979
46.4 mm (1.8 in)
1980
47.8 mm (1.9 in)
1981
44.2 mm (1.7 in)
1982
25.2 mm (1.0 in)
1983
56.2 mm (2.2 in)
1984
30.3 mm (1.2 in)
1985
35.8 mm (1.4 in)
1986
43.2 mm (1.7 in)
1987
70.8 mm (2.8 in)
1988
40.4 mm (1.6 in)
1989
49.0 mm (1.9 in)
1990
38.4 mm (1.5 in)
1991
32.3 mm (1.3 in)
1992
59.7 mm (2.4 in)
1993
59.7 mm (2.4 in)
1994
45.2 mm (1.8 in)
1995
40.9 mm (1.6 in)
1996
21.2 mm (0.8 in)
1997
43.4 mm (1.7 in)
1998
43.7 mm (1.7 in)
1999
65.4 mm (2.6 in)
2000
28.7 mm (1.1 in)
2001
41.1 mm (1.6 in)
2002
27.4 mm (1.1 in)
2003
50.8 mm (2.0 in)
2004
30.7 mm (1.2 in)
2005
62.8 mm (2.5 in)
2006
30.7 mm (1.2 in)
2007
32.5 mm (1.3 in)
2008
87.6 mm (3.4 in)
2009
32.6 mm (1.3 in)
2010
64.8 mm (2.6 in)
2011
57.5 mm (2.3 in)
2012
13.5 mm (0.5 in)
Longest dry spell (CDD)
The longest dry spell of the year at Thermopolis 21WNW, 1951 to 2012. The record is 69 days in 1964, marked on the chart; the median year is 32 days.
Longest dry spell (CDD) at Thermopolis 21WNW by year
Year
Longest dry spell (CDD)
1951
17 days
1952
40 days
1957
26 days
1958
41 days
1959
35 days
1960
37 days
1961
40 days
1962
30 days
1963
32 days
1964
69 days
1965
57 days
1966
39 days
1967
23 days
1968
28 days
1969
39 days
1970
39 days
1971
56 days
1972
31 days
1973
42 days
1974
37 days
1975
32 days
1976
31 days
1977
44 days
1978
30 days
1979
35 days
1980
32 days
1981
26 days
1982
40 days
1983
16 days
1984
40 days
1985
26 days
1986
24 days
1987
39 days
1988
45 days
1989
39 days
1990
31 days
1991
39 days
1992
32 days
1993
36 days
1994
29 days
1995
21 days
1996
21 days
1997
30 days
1998
26 days
1999
23 days
2000
26 days
2001
33 days
2002
34 days
2003
21 days
2004
32 days
2005
28 days
2006
36 days
2007
54 days
2008
69 days
2009
24 days
2010
30 days
2011
24 days
2012
23 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 Thermopolis 21WNW falls on 10 June and the median first autumn frost on 4 September, which leaves a median of 91 days between them.
Fitted over all years, the growing season changes by +0.8 days per decade at this station.
Frost dates and growing season at Thermopolis 21WNW
Measure
Median, all years
Earliest period
Recent period (1963 to 2011)
Recent against earliest
Fitted trend
Last spring frost
10 June
n/a
12 June
n/a
+0.6 days per decade
First autumn frost
4 September
n/a
9 September
n/a
+1.5 days per decade
Growing days
91 days
n/a
89 days
n/a
+0.8 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
43 years, 1952 to 2011
A day with at least 30.4 mm (1.2 in) of rain is expected about once in 2 years. A day with at least 59.9 mm (2.4 in) of rain is expected about once in 100 years.
Rainfall return levels at Thermopolis 21WNW: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
30.4 mm (1.2 in)
5 years
39.1 mm (1.5 in)
10 years
44.5 mm (1.8 in)
25 years
51.0 mm (2.0 in)
50 years
55.6 mm (2.2 in)
Longer than the 43 years of record
100 years
59.9 mm (2.4 in)
Longer than the 43 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, 43 years of values from 1952 to 2011.
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: 53.3 mm (2.1 in) in 1993; 52.6 mm (2.1 in) in 1963; 50.8 mm (2.0 in) in 2003.
Download the Data
Data for Thermopolis 21WNW standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Thermopolis 21WNW 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 2026-10-16 (16 October 2026). Records are computed by this site and are not official.