Western and Central Wyoming

Weather Forecast Office

2018 Annual Climate Summaries

2018 Climate Summaries

Casper

Lander

Riverton

...Highlights of 2020...

Annual: 1st driest year on 81 years of record (1939-2020), with just 46.2 percent of normal precipitation, 20th snowiest year on record with 119 percent of normal annual snowfall. Highest wind gust was 75 mph on January 4th.
Monthly Temperatures: 10th coldest October on record.
Monthly Precipitation: 1st driest May (tie), 1st driest July, 4th driest August and 1st driest November (tie) on record.
Monthly Snowfall: 1st snowiest February and 4th snowiest September on record.

Temperatures

Winds

Precipitation

Snowfall

Temperature Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Average High	37.1	30.4	47.4	54.7	69.8	82.1	94.2	90.9	75.5	59.3	51.7	35.7	60.5
Mean High (1981-2010 Normals)	35.2	37.8	47.9	56.8	67.1	78.8	88.1	86.4	74.3	59.4	44.7	34.2	59.2
Average Low	18.1	12.6	24.5	23.4	36.3	45.7	52.2	51.9	40	26	22.5	16.8	30.8
Mean Low (1981-2010 Normals)	14.3	15.7	22.4	28.6	37.2	45.7	53.0	51.5	41.4	31.0	21.6	13.5	31.3
Average Temperature	27.6	21.5	36	39	53	63.9	71.7	71.4	57.8	42.6	37.1	26.3	45.7
Mean Average Temperature (1981-2010 Normals)	24.7	26.7	35.2	42.7	52.2	62.2	70.5	69.0	57.9	45.2	33.2	23.8	45.3
Departure from Normal	2.9	-5.2	0.8	-3.7	0.8	1.7	1.2	2.4	-0.1	-2.6	3.9	2.5	0.4
Rank: 81 years of record (P.O.R 12/1939-2020)	63	15	51	13	43	52	52	66	31	10	62	44	43

Highest Daily Maximum	49	44	60	78	91	94	100	98	98	82	73	53	100
Date of Occurrence	16	29	31	30	31	5	12	23	5	6	4	9	7/12
Lowest Daily Minimum	3	-6	6	-5	22	31	41	33	24	-8	4	-9	-9
Date of Occurrence	10	13	1	3	8	18	2	31	9	25	21	28	12/28
Number of Days with:	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Maximum >= 90°	0	0	0	0	1	5	19	25	4	0	0	0	54
Maximum <= 32°	5	18	5	4	0	0	0	0	0	2	1	14	49
Minimum <= 32°	31	28	28	24	10	1	0	0	6	18	23	29	198
Minimum <= 0°	0	2	0	2	0	0	0	0	0	3	0	3	10
Record High Temperatures Set or Tied	0	0	0	0	1	2	0	2	2	1	4	0	11
Record Low Temperatures Set or Tied	0	0	0	3	2	1	0	1	3	5	0	0	15

Temperature Ranks and Records:

Daily Records:

Record High Temperatures:

May: 91 on the 31st.

June: 91 on the 1st and 94 on the 5th.
  August: 97 on the 17th (tie) and 98 on the 23rd.

  September: 98 on the 5th (ties all time high). 87 on the 24th (tie).

  October: 81 on the 8th.
  November: 71 on the 2nd (tie), 72 on the 3rd, 73 on the 4th, and 71 on the 5th (tie).

Record Low Temperatures:

April: -5 on the 3rd, 23 on the 12th, and 7 on the 13th.
May: 29 on the 24th and 27 on the 25th.
June: 31 on the 18th.

August: 33 on the31st (tie).
September: 29 on the 8th (tie), 24 on the 9th, and 27 on the 10th.

October: 9 on the 22nd, -5 on the 23rd, 10 on the 24th, 8 on the 25th and -6 on the 26th.

Coldest Months of October on Record
Rank	Year	Average Temperature °F
1	2019	36.8
2	2009	37.0
3	1969	37.8
4	2002	38.3
5	1984	40.1
6	1949	41.0
7	1970	41.2
8	2013	41.5
9	1946	41.8
10	2020	42.3

Top Ten Warmest Years on Record
Rank	Year	Average Temperature °F
1	1994	49.1
2	2012	48.7
3	1954	48.3
4	1981	48.1
5	1992	48.0
6	1940, 1953, 1963	47.3
9	2015, 2006, 1999	47.1
40	2020	45.7

Top Ten Coldest Years on Record
Rank	Year	Average Temperature °F
1	1985	42.5
2	1951	43.1
3	1978	43.2
4	1964	43.5
5	2019, 1975	43.6
6	2009, 1979, 1968, 1949	43.8
10	1971	43.9
43	2020	45.7


Average Annual Temperature for Period of Record - Click on Graph to Enlarge

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Wind Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Average Speed (MPH)	16.8	15.7	13.8	11.1	11	11.8	10	9	10.4	12.4	16.4	16	12.9
Maximum 3-sec Gust	75	57	62	54	59	70	55	61	53	57	72	53	75
Direction	210	230	260	220	230	220	220	220	250	310	210	210	210
Date of Occurrence	4	14	11	6	31	6	7	24	19	11	8	22	1/4
Number of Days with:
2-Min Wind >50 mph	1	0	1	0	0	0	0	0	0	0	0	0	2
Peak Wind >50 mph	6	3	2	3	4	10	6	5	1	5	9	3	57
Peak Wind >70 mph	1	0	0	0	0	1	0	0	0	0	1	0	3

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Precipitation Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Total (inches)	0.48	0.82	0.96	1.28	0.3	0.3	0.02	0.05	0.54	0.32	0.04	0.68	5.79
Mean Precipitation (1981-2010 Normals)	0.51	0.57	0.82	1.29	2.02	1.61	1.41	0.85	1.08	1.11	0.76	0.49	12.52
Departure from Normal	-0.03	0.25	0.14	-0.01	-1.72	-1.31	-1.39	-0.8	-0.54	-0.79	-0.72	0.19	-6.73
Percent of Normal	94	144	117	99	15	19	1	6	50	29	5	139	46
Rank - 81 years (P.O.R 12/1939-2020)	41	70	50	44	1	11	1	4	35	13	1	56	1

Greatest 24-HR Total	0.16	0.24	0.24	0.42	0.15	0.17	0.02	0.02	0.32	0.13	0.02	0.23	0.42
Dates of Occurrence	29	3	25	23	4	6	29	3, 6	7	22	14	22-23	4/23
Number of Days with:
Precipitation >= 0.01	6	10	8	9	6	5	1	3	3	7	3	10	71
Precipitation >= 0.10	2	4	5	5	1	1	0	0	2	1	0	3	24
Precipitation >= 1.00	0	0	0	0	0	0	0	0	0	0	0	0	0
Days with Thunderstorms	0	0	0	3	2	7	4	10	0	0	0	0	26
Daily Precipitation Records Set or Tied	0	0	0	0	0	0	0	0	0	0	0	1	1

Precipitation Ranks and Records:

One Day Precipitation Records:

December: 0.22" on the 22nd.

Top Ten Driest May's on Record
Rank	Year	Precipitation (inches)
1	2020	0.30
1	1966	0.30
3	1994	0.37
4	2009	0.43
5	2014	0.49
6	2003	0.51
7	1960	0.56
8	1974	0.62
9	2001	0.63
10	1954	0.70

Top Ten Driest July's on Record
Rank	Year	Precipitation (inches)
1	2020	0.02
2	1991	0.09
3	1971	0.11
4	2000	0.22
5	2016	0.24
5	1999	0.24
7	1959	0.27
7	1955	0.27
9	1989	0.28
10	2017	0.37

Top Ten Driest August's on Record
Rank	Year	Precipitation (inches)
1	1944	Trace
2	1950	0.02
3	1995	0.04
4	2020	0.05
5	1961	0.08
6	1943	0.09
6	1985	0.09
8	1951	0.10
9	1971	0.11
9	1999	0.11

Top Ten Driest November's on Record
Rank	Year	Precipitation (inches)
1	1949	0.04
1	2020	0.04
3	2007	0.05
3	2009	0.05
5	1965	0.07
6	1997	0.08
7	1976	0.09
8	1951	0.20
8	2000	0.20
10	2013	0.24

Top Ten Driest Years on Record
Rank	Year	Precipitation (inches)
1	2020	5.79
2	1988	6.56
3	2001	6.76
4	2002	7.05
5	1960	7.34
6	1954	7.70
7	2012	7.88
8	1963	7.90
9	1966	8.14
10	1943	8.91

Top Ten Wettest Years on Record
Rank	Year	Precipitation (inches)
1	1982	20.48
2	1995	18.94
3	1983	18.41
4	1978	17.64
5	1941	16.24
6	1957	16.12
7	1986	15.92
8	1993	15.91
9	2009	15.77
10	2016	15.57
81	2020	5.79


Annual Precipitation for Period of Record - Click on Graph to Enlarge

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Snow Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Total (inches)	7.9	28.4	15.1	15.2	0.001	0.001	0	0	7.5	3.7	0.4	11	89.2
Mean Snowfall (1981-2010 Normals)	9.1	9.8	10.9	11.6	2.9	0.1	0.0	0.0	1.8	7.4	10.3	11.0	74.9
Departure from Normal	-1.2	18.6	4.2	3.6	-2.9	0.1	0.0	0.0	5.7	-3.7	-9.9	0	14.3
Percent of Normal	87	290	139	131	0	1	0	0	417	50	4	100	119
Rank - Least to Most 81 years (P.O.R 12/1939-2020)	30	81	62	58	29	NA	NA	NA	78	31	3	50	63

Greatest 24-HR Total	2.6	15.2	4.1	4.9	T	0.0	0.0	0	5.2	2.3	0..4	3.2	15.2
Dates of Occurrence	27	3	12	1	9	NA	NA	NA		20	25	8	2/3
Number of Days with:
Snowfall >= 1.0 inch	3	3	6	5	0	0	0	0	2	2	0	3	24
Daily Snowfall Records Set or Tied	0	0	0	0	0	0	0	0	1	0	0	0	1
* 50 months of September on record with no snowfall.

Snowfall Ranks and Records:

One Day Snowfall Records (inches):

September: 5.2" on the 8th.

Snowiest Months of February on Record
Rank	Year	Snowfall (inches)
1	2020	28.4
2	1952	23.8
3	1987	22.7
4	1989	21.5
4	1955	21.5
6	2004	18.9
7	2018	18.6
8	1953	18.5
9	1995	16.9
10	1976	16.1

Snowiest Months of October on Record
Rank	Year	Snowfall (inches)
1	2000	11.5
1	1982	11.5
3	1965	8.8
4	2020	7.5
5	1995	7.1
6	1985	7.0
7	1961	6.3
8	1974	5.1
9	1994	4.9
10	2013	4.8

Top Ten Snowiest Years on Record
Rank	Year	Snowfall (inches)
1	1982	137.6
2	1975	124.0
3	1984	121.2
4	1973	118.3
5	1983	114.2
6	1978	112.7
7	2013	107.5
8	1955	103.3
9	1979	103.0
10	1985	101.0
20	2020	89.2



Annual and Seasonal Snowfall for Period of Record - Click on Graph to Enlarge

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Lander Climate Summary Banner

Click Here for the complete 2018 summary for Lander

...Highlights of 2018...

Annual - 37th warmest year (above normal) on 127 years of record (1892-2018).
59th wettest year on record with 106% of normal precipitation.
22nd least snowiest year on record with 57.3 inches (63 percent of normal).
The peak wind gust for the year was 68 mph on the peak wind gust which occurred on January 30th and April 16th.
Seasonal: 4th least snowiest Spring (March, April, May) on record with only 11.2 inches.
Monthly Precipitation: 10th driest September on record (0.05" of precipitation).

...Highlights of 2020...

Annual: Average temperature just 0.3 degrees below normal in 2020. Much drier than normal precipitation, with only 67 percent of normal. Above average snowfall, with 166 percent of normal.
- Average annual temperature 44.2 degrees was the 33rd coldest year on 103 years of record (1918-2020).
- 2020 precipitation total was 5.62 inches which was the 7th driest year on 103 years of record (1918-2020).
- 2020 snowfall total was 61.7 inches which was the 5th snowiest year on 103 years of record .
Seasonal: The 2019-2020 Seasonal Snow total was 66.7 inches, the 4th snowiest season on record.
Monthly Temperatures: 6th warmest August on record.
Monthly Precipitation: 4th wettest February on record. 8th driest May (tie), 6th driest August, and 8th driest November (tie) on record.
Monthly Snowfall: 2nd snowiest February, 7th snowiest April and 7th snowiest September on record.

Temperature

Precipitation

Snowfall

Temperature Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Average High	31.6	24.9	47.6	56.1	71.3	80.5	89.2	90.6	75.3	59.6	49.1	33.8	59.1
Mean High (1981-2010 Normals)	31.0	37.4	49.6	60.3	69.2	79.4	88.2	86.7	74.9	60.0	43.1	29.5	59.1
Average Low	6.6	1.2	21.9	27.4	41.1	50.1	53.7	53.0	41.5	27.5	16.9	7.8	29.1
Mean Low (1981-2010 Normals)	6.2	11.0	22.5	30.6	40.1	48.1	54.0	51.4	41.4	30.0	17.6	5.4	29.9
Average Temperature	19.1	13.0	34.8	41.8	56.2	65.3	71.5	71.8	58.4	43.1	33.0	22.2	44.2
Mean Average Temperature (1981-2010 Normals)	18.6	24.2	36.1	45.4	54.6	63.8	71.1	69.0	58.2	45.0	30.3	17.4	44.5
Departure from Normal	0.5	-11.2	-1.3	-3.6	1.6	1.5	0.4	2.8	0.2	-1.9	2.7	4.8	-0.3
Rank: Coldest to Warmest 103 years of record (P.O.R 12/1918-2020)	66	13	57	23	78	73	68	97	62	26	78	78	66
Highest Daily Maximum	44	50	59	77	90	95	97	96	97	84	72	53	97
Date of Occurrence	8	2	31	30	31	6	13	7,18	6	7	6	23	7/13, 9/6
Lowest Daily Minimum	-5	-16	-2	2	28	39	44	38	26	-12	1	-6	-16
Date of Occurrence	16	20,21	2	3	5	8	1	31	9	26	30	13	2/20, 2/21
Number of Days with:
Maximum >= 90°	0	0	0	0	1	6	16	23	1	0	0	0	47
Maximum <= 32°	19	4	1	2	0	0	0	0	0	3	0	13	42
Minimum <= 32°	31	29	30	21	5	0	0	0	5	18	27	31	197
Minimum <= 0°	5	12	1	0	0	0	0	0	0	1	0	4	23
Record Highs Set or Tied	0	0	0	0	0	1	0	1	1	0	1	0	7
Record Lows Set or Tied	0	0	0	0	0	0	0	0	0	1	0	0	1
* Multiple day occurrence

Temperature Ranks and Records:

Daily Records:

Max:

June: ^{78 on the 13th.}

August: ^{96 on the 18th (tie).}

September: ^{97 on the 6th.}

November: ^{64 on the 19th.}

Min:

October: -12th the 26th.

Top Ten Warmest August's on Record
Rank	Year	Average Temperature °F
1	2003	73.8
2	2013	73.0
2	2000	73.0
4	2001	72.9
5	2012	71.9
6	2020	71.8
6	2011	71.8
8	2007	71.6
9	1922	71.3
10	1999	71.0

Warmest Years on Record (101 Years)
Rank	Year	Average Temperature °F
1	2012	48.5
2	2006, 1999	47.0
4	1934	46.9
5	2007	46.5
6	2005, 1981	46.3
8	1954	46.2
9	2015	45.9
10	1953	45.8
33	2020	44.2

Top Ten Coldest Years on Record
Rank	Year	Average Temperature °F
1	1993	38.8
2	1924	39.5
3	1984, 1944	39.7
5	1978	40.1
6	1985	40.3
7	1968, 1929	40.5
9	1975	40.8
10	1986, 1932	41.0
66	2020	44.2


Average Annual Temperature for Period of Record - Click on Graph to Enlarge

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Precipitation Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Total (inches)	0.29	0.98	0.24	1.84	0.34	0.41	0.25	0.001	0.7	0.18	0.03	0.36	5.62
Mean Precipitation (1981-2010 Normals)	0.28	0.34	0.56	0.98	1.45	1.21	0.78	0.50	0.83	0.85	0.41	0.24	8.42
Departure from Normal	0.01	0.64	-0.32	0.86	-1.11	-0.8	-0.53	-0.50	-0.13	-0.67	-0.38	0.12	-2.8
Percent of Normal	104	288	43	188	23	34	32	0	84	21	7	150	67
Rank - Driest to Wettest 103 years (P.O.R. 1918-2020)	72	98	34	82	8 Tie	24	29	6	60	16	8 Tie	78	7

Greatest 24-HR Total	0.2	0.42	0.12	0.64	0.26	0.19	0.13	T	0.63	0.1	0.03	0.12	0.64
Dates of Occurrence	28	3	2	12	31	7	1	8,19,20,26	8	25	8	15	4/12
Number of Days with:
Precipitation >= 0.01	3	7	4	8	4	6	3	0	3	3	1	7	49
Precipitation >= 0.10	1	3	1	4	1	1	1	0	1	1	0	1	15
Precipitation >= 1.00	0	0	0	0	0	0	0	0	0	0	0	0	0
Daily Precipitation Records Set or Tied	0	0	0	1	0	0	0	0	0	0	0	0	1

Precipitation Ranks and Records:

One Day Precipitation Records:

April: 0.64" on the 12th.

Top Ten Wettest February's on Record
Rank	Year	Precipitation (inches)
1	2004	1.33
2	2015	1.28
3	2003	1.15
4	2020	0.98
5	1986	0.97
6	2017	0.96
7	1955	0.90
8	1935	0.86
9	1920	0.80
10	2011	0.75

Top Ten Driest May's on Record
Rank	Year	Precipitation (inches)
1	1936	0.08
2	1963	0.11
3	1994	0.17
4	1984	0.18
5	1974	0.20
6	2006	0.26
7	2001	0.31
8	1969	0.34
8	2020	0.34
10	1948	0.35

Top Ten Driest August's on Record
Rank	Year	Precipitation (inches)
1	1929	0
1	1944	0
1	1949	0
1	1969	0
1	1985	0
6	2020	0.001
7	1937	0.01
7	1967	0.01
9	1924	0.02
10	1956	0.02

Top Ten Driest November's on Record
Rank	Year	Precipitation (inches)
1	1939	0
1	1949	0
1	1976	0
1	1989	0
5	1981	0.01
5	1982	0.01
5	2009	0.01
8	1954	0.03
8	2020	0.03
10	1988	0.04

Top Ten Driest Years on Record
Rank	Year	Precipitation (inches)
1	1988	3.75
2	2012	3.98
3	1974	4.12
4	1954	4.85
5	2001, 2006	5.07
7	2020	5.62
8	1966	5.66
9	1990	5.71
10	1922	5.91

Top Ten Wettest Years on Record
Rank	Year	Precipitation (inches)
1	1923	18.43
2	2017	15.86
3	2016	15.24
4	1941	14.74
5	1912	14.73
6	1993	13.49
7	1998, 1995	13.41
9	1971	13.11
10	1947	12.45
97	2020	5.62


Annual Precipitation for Period of Record - Click on Graph to Enlarge

Click on Graph to Enlarge

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Snow Banner

Element	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Total (inches)	4	19.5	4.4	20.3	0.01	0	0	0	3.3	3.8	0.001	6.4	61.7
Mean Snowfall (1981-2010 Normals)	4.8	6.0	5.9	6.1	1.2	0.0	0.0	0.0	0.3	3.7	4.3	4.8	37.1
Departure from Normal	-0.8	13.5	-1.5	14.2	-1.19	0.0	0.0	0.0	3	0.1	-4.3	1.6	24.6
Percent of Normal	83	325	75	333	1	0	0	0	1100	103	0	133	166
Rank - Least to Most 103 years (P.O.R 1918-2020)	57	97	82	94	70	NA	NA	NA	95	66	15	71	100

Greatest 24-HR Total	2.5	9	2	8	T	0	0	0	2.9	2.5	T	2.3	2.9
Dates of Occurrence	28	3	2	12	31	NA	NA	NA	8	25	9,10	15	9/8
Number of Days with:
Snowfall >= 1.0 inch	1	5	3	4	0	0	0	0	1	2	0	3	19
Daily Snowfall Records Set or Tied	0	0	0	1	0	0	0	0	2	0	0	0	3
* 69 months of May on record a trace or 0.0" of snowfall. * 83 months of September on record with no snowfall.

Snowfall Ranks and Records:

One Day Snowfall Records (inches):

April: 8.0" on the 12th.
September: 2.9" on the 8th, and 0.4" on the 9th.

Top Ten Snowiest February's on Record
Rank	Year	Snowfall (inches)
1	1986	22.5
2	2020	19.5
3	2014	17.8
4	2003	16.9
5	1958	16.0
6	2002	15.3
7	2016	15.1
8	1964	13.5
9	1934,1919	13.0

Top Ten Snowiest April's on Record
Rank	Year	Snowfall (inches)
1	1998	31.7
2	1919	29.0
3	2012	24.7
4	1944	22.1
5	1921	21.0
6	2016	20.9
7	2020	20.3
8	1926	18.0
9	1978, 1933	17.0

Top Ten Snowiest September's on Record
Rank	Year	Snowfall (inches)
1	1982	13.0
2	2013	5.7
2	2000	5.7
4	1965	5.0
5	1946	4.0
5	1944	4.0
7	2020	3.3
8	1929	3.0
9	1999	2.8
10	1945	2.0

Top Ten Snowiest Years on Record
Rank	Year	Snowfall (inches)
1	1920	77.0
2	2017	71.1
3	2013	70.6
4	2009	62.5
5	2020	61.7
5	2016	61.7
7	2010	60.1
8	1919	58.0
9	1923	56.2
10	1944	55.4



Annual and Seasonal Snowfall for Period of Record - Click on Graph to Enlarge

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Numbers 5 through 2	Number 1: The Roosevelt Fire