Record envelope, standing records and threshold days for Mt Diablo Junction (USC00045915), California, United States, with 75 years of record.
Key Facts for Mt Diablo Junction
Mt Diablo Junction (USC00045915) is a weather station in California, United States at 37.88 latitude and -121.93 longitude, 661 m (2,170 ft) above sea level.
The station reports from 1952 to 2026, 75 years of record.
1,464 records set at Mt Diablo Junction still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Mt Diablo Junction set a daily record precipitation of 19.8 mm (0.8 in) on 21 April 2026.
About the Station
Location: California, United States, 37.88 latitude, -121.93 longitude.
Elevation: 661 m (2,170 ft).
Period of record: 1952 to 2026, 75 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.
Daily Record Envelope and 2026
10 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 Mt Diablo Junction. The lines show the 2026 daily maximum and minimum. 10 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.
Daily record high and record low at Mt Diablo Junction, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
25.0 C (77.0 F)
-7.8 C (18.0 F)
21.1 C (70.0 F)
1.7 C (35.1 F)
Feb
26.7 C (80.1 F)
-10.0 C (14.0 F)
22.8 C (73.0 F)
-0.6 C (30.9 F)
Mar
30.0 C (86.0 F)
-5.0 C (23.0 F)
30.0 C (86.0 F)
6.7 C (44.1 F)
Apr
35.6 C (96.1 F)
-5.0 C (23.0 F)
25.6 C (78.1 F)
4.4 C (39.9 F)
May
38.9 C (102.0 F)
-0.6 C (30.9 F)
31.7 C (89.1 F)
6.7 C (44.1 F)
Jun
41.7 C (107.1 F)
1.1 C (34.0 F)
33.9 C (93.0 F)
8.3 C (46.9 F)
Jul
43.9 C (111.0 F)
1.1 C (34.0 F)
34.4 C (93.9 F)
8.3 C (46.9 F)
Aug
41.7 C (107.1 F)
4.4 C (39.9 F)
35.6 C (96.1 F)
10.0 C (50.0 F)
Sep
41.7 C (107.1 F)
1.7 C (35.1 F)
n/a
n/a
Oct
37.8 C (100.0 F)
-1.1 C (30.0 F)
n/a
n/a
Nov
32.2 C (90.0 F)
-3.3 C (26.1 F)
n/a
n/a
Dec
25.0 C (77.0 F)
-10.0 C (14.0 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Mt Diablo Junction still stand. 2008 holds the most, with 47.
Standing records at Mt Diablo Junction by the year they were set
Year set
Standing records
1952
17
1953
25
1954
23
1955
28
1956
37
1957
19
1958
16
1959
16
1960
23
1961
22
1962
26
1963
11
1964
26
1965
16
1966
22
1967
37
1968
10
1969
9
1970
19
1971
28
1972
34
1973
19
1974
30
1975
22
1976
30
1977
27
1978
16
1979
12
1980
12
1981
7
1982
14
1983
9
1984
9
1985
18
1986
10
1987
20
1988
27
1989
36
1990
28
1991
22
1992
3
1993
6
1994
14
1995
21
1996
22
1997
4
1998
20
1999
13
2000
19
2001
29
2002
7
2003
12
2004
20
2005
10
2006
24
2007
43
2008
47
2009
29
2010
28
2011
23
2012
17
2013
10
2014
9
2015
16
2016
9
2017
26
2018
10
2019
19
2020
13
2021
15
2022
18
2023
18
2024
12
2025
18
2026
28
All-Time Record Progression
5 new records
5 all-time records were set at Mt Diablo Junction between 28 December 1988 and 25 October 2021. Each dot is a new record.
When Mt Diablo Junction set new all-time records
Date
Kind
Detail
1988-12-28
Record low maximum temperature
Record low maximum temperature -0.6 C (30.9 F)
1989-02-05
Record low minimum temperature
Record low minimum temperature -8.9 C (16.0 F)
1989-02-06
Record low minimum temperature
Record low minimum temperature -10.0 C (14.0 F)
2001-02-12
Record snow depth
Record snow depth 10.2 cm (4.0 in)
2021-10-25
Record daily precipitation
Record daily precipitation 153.4 mm (6.0 in)
Wettest Day of Each Month
Oct: 153.4 mm (6.0 in)
The wettest day on record for each calendar month at Mt Diablo Junction. The most was 153.4 mm (6.0 in) on 25 October 2021.
Record daily precipitation for each month at Mt Diablo Junction
Month
Record daily precipitation (mm)
Date
Jan
127.5 mm (5.0 in)
21 January 1967
Feb
120.1 mm (4.7 in)
1 February 1963
Mar
69.1 mm (2.7 in)
10 March 2023
Apr
63.5 mm (2.5 in)
7 April 2018
May
41.9 mm (1.6 in)
16 May 1996
Jun
29.2 mm (1.1 in)
5 June 2011
Jul
14.0 mm (0.6 in)
9 July 1974
Aug
15.5 mm (0.6 in)
19 August 1976
Sep
51.1 mm (2.0 in)
19 September 1959
Oct
153.4 mm (6.0 in)
25 October 2021
Nov
91.4 mm (3.6 in)
6 November 1994
Dec
123.2 mm (4.9 in)
23 December 1955
Period of Record Coverage
1952 to 2026
Complete yearUnder 90 percent of days
75 years of record at Mt Diablo Junction, 1952 to 2026. 5 years have data for under 90 percent of days and are left out of rankings: 1952, 1986, 1987, 1988, 2026.
Cooler than the station meanWarmer than the station mean
One stripe for each of 67 complete years at Mt Diablo Junction, 1953 to 2025. Blue stripes are years cooler than the station's own mean of 14.8 C (58.6 F); red stripes are warmer. The coolest year was 2007, at 13.4 C (56.0 F), and the warmest was 1959, at 16.3 C (61.3 F). The strongest colour marks a difference of 1.6 C (2.9 F).
Annual mean temperature at Mt Diablo Junction as warming stripes, 1953 to 2025
Year
Annual mean temperature
Difference from the station mean
1953
14.4 C
-0.43 C
1954
14.6 C
-0.22 C
1955
14.0 C
-0.79 C
1956
14.4 C
-0.36 C
1957
14.4 C
-0.38 C
1959
16.3 C
+1.51 C
1960
15.1 C
+0.29 C
1961
15.1 C
+0.33 C
1962
14.8 C
+0.02 C
1963
14.4 C
-0.44 C
1964
14.6 C
-0.22 C
1965
14.8 C
+0.03 C
1966
15.9 C
+1.13 C
1967
15.9 C
+1.13 C
1968
15.1 C
+0.34 C
1969
15.2 C
+0.42 C
1970
15.7 C
+0.92 C
1971
14.6 C
-0.20 C
1972
14.8 C
+0.00 C
1973
14.3 C
-0.50 C
1974
14.5 C
-0.28 C
1975
14.7 C
-0.12 C
1977
16.0 C
+1.22 C
1978
15.7 C
+0.89 C
1979
15.3 C
+0.49 C
1981
15.5 C
+0.70 C
1982
13.6 C
-1.19 C
1983
14.2 C
-0.56 C
1984
15.2 C
+0.38 C
1985
14.6 C
-0.19 C
1989
14.3 C
-0.46 C
1990
14.7 C
-0.06 C
1991
14.8 C
+0.03 C
1992
15.4 C
+0.58 C
1993
14.5 C
-0.25 C
1994
14.0 C
-0.75 C
1995
14.4 C
-0.41 C
1996
15.8 C
+1.03 C
1997
15.4 C
+0.63 C
1998
13.4 C
-1.39 C
1999
14.5 C
-0.34 C
2000
14.1 C
-0.72 C
2001
14.1 C
-0.68 C
2002
14.8 C
+0.00 C
2003
14.7 C
-0.11 C
2004
14.2 C
-0.55 C
2005
14.0 C
-0.77 C
2006
13.7 C
-1.09 C
2007
13.4 C
-1.43 C
2008
14.1 C
-0.72 C
2009
14.5 C
-0.27 C
2010
13.7 C
-1.12 C
2011
13.8 C
-1.03 C
2012
14.6 C
-0.18 C
2013
15.1 C
+0.35 C
2014
16.1 C
+1.29 C
2015
15.7 C
+0.90 C
2016
15.2 C
+0.43 C
2017
15.4 C
+0.61 C
2018
15.1 C
+0.30 C
2019
14.5 C
-0.28 C
2020
16.0 C
+1.16 C
2021
15.3 C
+0.55 C
2022
15.5 C
+0.74 C
2023
13.8 C
-0.99 C
2024
15.3 C
+0.52 C
2025
15.3 C
+0.52 C
The fitted trend in annual mean temperature here over 1953 to 2025 is -0.02 C (-0.10 to 0.06) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: -0.03 F (-0.17 to 0.12) per decade. The slope is a straight line fitted to 67 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Mt Diablo Junction
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
-0.02 C (-0.10 to 0.06) per decade
-0.03 F (-0.17 to 0.12) per decade
1953 to 2025
67
Not clearly different from zero
Mean daily maximum
-0.2 C (-0.3 to -0.1) per decade
-0.3 F (-0.5 to -0.1) per decade
1953 to 2025
67
Fall
Mean daily minimum
0.14 C (0.03 to 0.25) per decade
0.3 F (0.1 to 0.5) per decade
1953 to 2025
67
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
1952 to 2026
Yearly extremes at Mt Diablo Junction: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
43.9 C (111.0 F)
1972
38.3 C (100.9 F)
75
Coldest night (TNn)
-10.0 C (14.0 F)
1989
-2.8 C (27.0 F)
75
Wettest day (Rx1day)
153.4 mm (6.0 in)
2021
54.6 mm (2.1 in)
75
Wettest five days (Rx5day)
277.7 mm (10.9 in)
1955
101.6 mm (4.0 in)
75
Longest dry spell (CDD)
179 days
2003
117 days
75
Hottest day (TXx)
The hottest day of the year at Mt Diablo Junction, 1952 to 2026. The record is 43.9 C (111.0 F) in 1972, marked on the chart; the median year is 38.3 C (100.9 F).
Hottest day (TXx) at Mt Diablo Junction by year
Year
Hottest day (TXx)
1952
37.8 C (100.0 F)
1953
38.3 C (100.9 F)
1954
40.0 C (104.0 F)
1955
41.7 C (107.1 F)
1956
40.0 C (104.0 F)
1957
40.6 C (105.1 F)
1958
38.3 C (100.9 F)
1959
40.6 C (105.1 F)
1960
41.7 C (107.1 F)
1961
41.7 C (107.1 F)
1962
37.8 C (100.0 F)
1963
40.6 C (105.1 F)
1964
40.0 C (104.0 F)
1965
37.8 C (100.0 F)
1966
41.7 C (107.1 F)
1967
40.0 C (104.0 F)
1968
37.8 C (100.0 F)
1969
38.3 C (100.9 F)
1970
40.0 C (104.0 F)
1971
41.7 C (107.1 F)
1972
43.9 C (111.0 F)
1973
40.0 C (104.0 F)
1974
37.8 C (100.0 F)
1975
40.6 C (105.1 F)
1976
39.4 C (102.9 F)
1977
41.1 C (106.0 F)
1978
41.7 C (107.1 F)
1979
39.4 C (102.9 F)
1980
38.3 C (100.9 F)
1981
38.9 C (102.0 F)
1982
35.0 C (95.0 F)
1983
37.2 C (99.0 F)
1984
40.0 C (104.0 F)
1985
36.7 C (98.1 F)
1986
35.0 C (95.0 F)
1987
38.9 C (102.0 F)
1988
41.7 C (107.1 F)
1989
37.8 C (100.0 F)
1990
38.3 C (100.9 F)
1991
38.9 C (102.0 F)
1992
37.8 C (100.0 F)
1993
38.3 C (100.9 F)
1994
36.7 C (98.1 F)
1995
37.2 C (99.0 F)
1996
39.4 C (102.9 F)
1997
37.8 C (100.0 F)
1998
40.6 C (105.1 F)
1999
38.3 C (100.9 F)
2000
37.2 C (99.0 F)
2001
38.9 C (102.0 F)
2002
40.6 C (105.1 F)
2003
38.3 C (100.9 F)
2004
36.7 C (98.1 F)
2005
37.2 C (99.0 F)
2006
41.7 C (107.1 F)
2007
38.3 C (100.9 F)
2008
41.1 C (106.0 F)
2009
36.7 C (98.1 F)
2010
37.2 C (99.0 F)
2011
33.3 C (91.9 F)
2012
37.2 C (99.0 F)
2013
37.8 C (100.0 F)
2014
35.0 C (95.0 F)
2015
37.2 C (99.0 F)
2016
35.0 C (95.0 F)
2017
38.3 C (100.9 F)
2018
33.9 C (93.0 F)
2019
35.0 C (95.0 F)
2020
39.4 C (102.9 F)
2021
37.2 C (99.0 F)
2022
40.0 C (104.0 F)
2023
35.0 C (95.0 F)
2024
39.4 C (102.9 F)
2025
35.0 C (95.0 F)
2026
35.6 C (96.1 F)
Coldest night (TNn)
The coldest night of the year at Mt Diablo Junction, 1952 to 2026. The record is -10.0 C (14.0 F) in 1989, marked on the chart; the median year is -2.8 C (27.0 F).
Coldest night (TNn) at Mt Diablo Junction by year
Year
Coldest night (TNn)
1952
-1.1 C (30.0 F)
1953
-1.7 C (28.9 F)
1954
-1.1 C (30.0 F)
1955
-2.2 C (28.0 F)
1956
-7.2 C (19.0 F)
1957
-6.7 C (19.9 F)
1958
-3.9 C (25.0 F)
1959
-1.7 C (28.9 F)
1960
-4.4 C (24.1 F)
1961
-0.6 C (30.9 F)
1962
-7.8 C (18.0 F)
1963
-4.4 C (24.1 F)
1964
-2.2 C (28.0 F)
1965
-2.2 C (28.0 F)
1966
-2.2 C (28.0 F)
1967
-5.6 C (21.9 F)
1968
-2.8 C (27.0 F)
1969
-3.9 C (25.0 F)
1970
-0.6 C (30.9 F)
1971
-1.7 C (28.9 F)
1972
-7.8 C (18.0 F)
1973
-1.1 C (30.0 F)
1974
-3.3 C (26.1 F)
1975
-3.9 C (25.0 F)
1976
-3.3 C (26.1 F)
1977
-1.1 C (30.0 F)
1978
-2.2 C (28.0 F)
1979
-1.7 C (28.9 F)
1980
-2.8 C (27.0 F)
1981
0.6 C (33.1 F)
1982
-2.8 C (27.0 F)
1983
0.0 C (32.0 F)
1984
-2.2 C (28.0 F)
1985
-3.3 C (26.1 F)
1986
-0.6 C (30.9 F)
1987
-3.3 C (26.1 F)
1988
-5.0 C (23.0 F)
1989
-10.0 C (14.0 F)
1990
-10.0 C (14.0 F)
1991
-5.0 C (23.0 F)
1992
-2.2 C (28.0 F)
1993
-2.8 C (27.0 F)
1994
-2.8 C (27.0 F)
1995
-2.2 C (28.0 F)
1996
-1.7 C (28.9 F)
1997
-5.0 C (23.0 F)
1998
-3.9 C (25.0 F)
1999
-3.9 C (25.0 F)
2000
-2.2 C (28.0 F)
2001
-3.3 C (26.1 F)
2002
-3.9 C (25.0 F)
2003
-3.3 C (26.1 F)
2004
-3.3 C (26.1 F)
2005
-1.7 C (28.9 F)
2006
-4.4 C (24.1 F)
2007
-5.6 C (21.9 F)
2008
-5.0 C (23.0 F)
2009
-5.0 C (23.0 F)
2010
-5.0 C (23.0 F)
2011
-5.0 C (23.0 F)
2012
-2.8 C (27.0 F)
2013
-5.0 C (23.0 F)
2014
-1.7 C (28.9 F)
2015
-2.2 C (28.0 F)
2016
-1.1 C (30.0 F)
2017
-2.2 C (28.0 F)
2018
-2.8 C (27.0 F)
2019
-1.7 C (28.9 F)
2020
-0.6 C (30.9 F)
2021
-1.7 C (28.9 F)
2022
-0.6 C (30.9 F)
2023
-2.8 C (27.0 F)
2024
-1.1 C (30.0 F)
2025
-0.6 C (30.9 F)
2026
-0.6 C (30.9 F)
Wettest day (Rx1day)
The wettest day of the year at Mt Diablo Junction, 1952 to 2026. The record is 153.4 mm (6.0 in) in 2021, marked on the chart; the median year is 54.6 mm (2.1 in).
Wettest day (Rx1day) at Mt Diablo Junction by year
Year
Wettest day (Rx1day)
1952
68.8 mm (2.7 in)
1953
28.7 mm (1.1 in)
1954
49.5 mm (1.9 in)
1955
123.2 mm (4.9 in)
1956
41.4 mm (1.6 in)
1957
40.6 mm (1.6 in)
1958
68.1 mm (2.7 in)
1959
51.1 mm (2.0 in)
1960
41.4 mm (1.6 in)
1961
46.7 mm (1.8 in)
1962
121.9 mm (4.8 in)
1963
120.1 mm (4.7 in)
1964
65.8 mm (2.6 in)
1965
32.5 mm (1.3 in)
1966
34.0 mm (1.3 in)
1967
127.5 mm (5.0 in)
1968
51.1 mm (2.0 in)
1969
80.0 mm (3.1 in)
1970
68.6 mm (2.7 in)
1971
37.1 mm (1.5 in)
1972
34.8 mm (1.4 in)
1973
43.7 mm (1.7 in)
1974
31.5 mm (1.2 in)
1975
40.4 mm (1.6 in)
1976
23.1 mm (0.9 in)
1977
55.4 mm (2.2 in)
1978
49.0 mm (1.9 in)
1979
45.7 mm (1.8 in)
1980
51.8 mm (2.0 in)
1981
68.6 mm (2.7 in)
1982
101.6 mm (4.0 in)
1983
53.3 mm (2.1 in)
1984
38.9 mm (1.5 in)
1985
57.2 mm (2.3 in)
1986
61.7 mm (2.4 in)
1987
81.3 mm (3.2 in)
1988
34.5 mm (1.4 in)
1989
33.0 mm (1.3 in)
1990
38.1 mm (1.5 in)
1991
78.7 mm (3.1 in)
1992
50.8 mm (2.0 in)
1993
90.7 mm (3.6 in)
1994
91.4 mm (3.6 in)
1995
105.9 mm (4.2 in)
1996
48.3 mm (1.9 in)
1997
71.6 mm (2.8 in)
1998
98.8 mm (3.9 in)
1999
45.2 mm (1.8 in)
2000
82.3 mm (3.2 in)
2001
54.6 mm (2.1 in)
2002
67.1 mm (2.6 in)
2003
41.7 mm (1.6 in)
2004
43.7 mm (1.7 in)
2005
76.5 mm (3.0 in)
2006
36.8 mm (1.4 in)
2007
32.0 mm (1.3 in)
2008
75.7 mm (3.0 in)
2009
84.3 mm (3.3 in)
2010
70.1 mm (2.8 in)
2011
37.3 mm (1.5 in)
2012
73.2 mm (2.9 in)
2013
26.9 mm (1.1 in)
2014
92.7 mm (3.6 in)
2015
45.0 mm (1.8 in)
2016
61.2 mm (2.4 in)
2017
108.5 mm (4.3 in)
2018
63.5 mm (2.5 in)
2019
55.9 mm (2.2 in)
2020
21.8 mm (0.9 in)
2021
153.4 mm (6.0 in)
2022
92.5 mm (3.6 in)
2023
71.6 mm (2.8 in)
2024
40.9 mm (1.6 in)
2025
59.7 mm (2.4 in)
2026
24.4 mm (1.0 in)
Wettest five days (Rx5day)
The wettest five days of the year at Mt Diablo Junction, 1952 to 2026. The record is 277.7 mm (10.9 in) in 1955, marked on the chart; the median year is 101.6 mm (4.0 in).
Wettest five days (Rx5day) at Mt Diablo Junction by year
Year
Wettest five days (Rx5day)
1952
94.7 mm (3.7 in)
1953
42.1 mm (1.7 in)
1954
78.2 mm (3.1 in)
1955
277.7 mm (10.9 in)
1956
73.0 mm (2.9 in)
1957
94.0 mm (3.7 in)
1958
131.3 mm (5.2 in)
1959
97.7 mm (3.8 in)
1960
96.0 mm (3.8 in)
1961
81.0 mm (3.2 in)
1962
269.9 mm (10.6 in)
1963
212.3 mm (8.4 in)
1964
137.6 mm (5.4 in)
1965
64.8 mm (2.6 in)
1966
80.8 mm (3.2 in)
1967
221.7 mm (8.7 in)
1968
85.9 mm (3.4 in)
1969
144.5 mm (5.7 in)
1970
134.1 mm (5.3 in)
1971
70.2 mm (2.8 in)
1972
102.9 mm (4.1 in)
1973
113.9 mm (4.5 in)
1974
74.4 mm (2.9 in)
1975
80.8 mm (3.2 in)
1976
43.7 mm (1.7 in)
1977
79.0 mm (3.1 in)
1978
123.0 mm (4.8 in)
1979
121.9 mm (4.8 in)
1980
153.4 mm (6.0 in)
1981
101.6 mm (4.0 in)
1982
121.2 mm (4.8 in)
1983
87.9 mm (3.5 in)
1984
59.8 mm (2.4 in)
1985
58.7 mm (2.3 in)
1986
235.7 mm (9.3 in)
1987
93.8 mm (3.7 in)
1988
49.0 mm (1.9 in)
1989
63.3 mm (2.5 in)
1990
62.7 mm (2.5 in)
1991
103.5 mm (4.1 in)
1992
104.8 mm (4.1 in)
1993
140.5 mm (5.5 in)
1994
114.0 mm (4.5 in)
1995
181.6 mm (7.1 in)
1996
82.6 mm (3.3 in)
1997
142.4 mm (5.6 in)
1998
152.2 mm (6.0 in)
1999
85.6 mm (3.4 in)
2000
141.0 mm (5.6 in)
2001
98.4 mm (3.9 in)
2002
167.2 mm (6.6 in)
2003
49.3 mm (1.9 in)
2004
92.9 mm (3.7 in)
2005
102.3 mm (4.0 in)
2006
111.8 mm (4.4 in)
2007
72.3 mm (2.8 in)
2008
124.0 mm (4.9 in)
2009
141.7 mm (5.6 in)
2010
179.2 mm (7.1 in)
2011
82.2 mm (3.2 in)
2012
193.4 mm (7.6 in)
2013
39.6 mm (1.6 in)
2014
132.1 mm (5.2 in)
2015
91.7 mm (3.6 in)
2016
159.7 mm (6.3 in)
2017
254.4 mm (10.0 in)
2018
82.1 mm (3.2 in)
2019
114.5 mm (4.5 in)
2020
41.4 mm (1.6 in)
2021
227.3 mm (8.9 in)
2022
157.6 mm (6.2 in)
2023
251.5 mm (9.9 in)
2024
65.2 mm (2.6 in)
2025
95.8 mm (3.8 in)
2026
80.5 mm (3.2 in)
Longest dry spell (CDD)
The longest dry spell of the year at Mt Diablo Junction, 1952 to 2026. The record is 179 days in 2003, marked on the chart; the median year is 117 days.
Longest dry spell (CDD) at Mt Diablo Junction by year
Year
Longest dry spell (CDD)
1952
136 days
1953
56 days
1954
148 days
1955
127 days
1956
132 days
1957
109 days
1958
38 days
1959
125 days
1960
133 days
1961
41 days
1962
162 days
1963
124 days
1964
83 days
1965
176 days
1966
80 days
1967
103 days
1968
86 days
1969
121 days
1970
132 days
1971
120 days
1972
154 days
1973
161 days
1974
110 days
1975
58 days
1976
63 days
1977
112 days
1978
117 days
1979
158 days
1980
90 days
1981
128 days
1982
75 days
1983
104 days
1984
84 days
1985
76 days
1986
76 days
1987
153 days
1988
115 days
1989
104 days
1990
67 days
1991
70 days
1992
112 days
1993
122 days
1994
140 days
1995
166 days
1996
155 days
1997
50 days
1998
110 days
1999
98 days
2000
85 days
2001
90 days
2002
154 days
2003
179 days
2004
113 days
2005
95 days
2006
135 days
2007
140 days
2008
163 days
2009
130 days
2010
142 days
2011
88 days
2012
138 days
2013
88 days
2014
131 days
2015
105 days
2016
159 days
2017
130 days
2018
129 days
2019
114 days
2020
89 days
2021
174 days
2022
104 days
2023
173 days
2024
134 days
2025
139 days
2026
95 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
52 years with a frost
Across 52 years with a frost, the median last spring frost at Mt Diablo Junction falls on 30 March and the median first autumn frost on 30 November, which leaves a median of 241 days between them.
Fitted over all years, the growing season changes by +3.1 days per decade at this station.
Frost dates and growing season at Mt Diablo Junction
Measure
Median, all years
Earliest period
Recent period (1984 to 2022)
Recent against earliest
Fitted trend
Last spring frost
30 March
n/a
25 March
n/a
-3.3 days per decade
First autumn frost
30 November
n/a
28 November
n/a
-0.2 days per decade
Growing days
241 days
n/a
246 days
n/a
+3.1 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
71 years, 1953 to 2025
A day with at least 56.0 mm (2.2 in) of rain is expected about once in 2 years. A day with at least 164.0 mm (6.5 in) of rain is expected about once in 100 years.
Rainfall return levels at Mt Diablo Junction: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
56.0 mm (2.2 in)
5 years
81.0 mm (3.2 in)
10 years
99.1 mm (3.9 in)
25 years
123.7 mm (4.9 in)
50 years
143.3 mm (5.6 in)
100 years
164.0 mm (6.5 in)
Longer than the 71 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, 71 years of values from 1953 to 2025.
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: 153.4 mm (6.0 in) in 2021; 127.5 mm (5.0 in) in 1967; 123.2 mm (4.9 in) in 1955.
Station Changes
2 suspected
2 changes were suspected in the annual mean temperature of Mt Diablo Junction, at 1964 and 2000. Each is measured against neighbouring stations.
Relative to 5 neighbouring stations, the station's annual mean temperature from 1964 ran 0.5 C (0.8 F) higher than in the years before (possible change).
Relative to 5 neighbouring stations, the station's annual mean temperature from 2000 ran 0.5 C (0.9 F) lower than in the years before (possible change).
Suspected changes in the annual mean temperature at Mt Diablo Junction, against neighbouring stations
Year
Shift (C)
Shift (F)
Strength
Neighbours
1964
+0.5
+0.8
possible
5
2000
-0.5
-0.9
possible
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.
Climate Twins
2011 to 2025 against 1961 to 1990
Over 2011 to 2025, Mt Diablo Junction had a mean temperature of 15.1 C (59.2 F) and 630.4 mm (24.8 in) of rain a year. The 3 stations whose 1961 to 1990 climate was closest to that are Barcelona/Aeropuerto (Spain, 9,539 km away), Ajaccio (France, 9,835 km away) and Bastia (France, 9,814 km away).
Climate twins of Mt Diablo Junction: stations whose 1961 to 1990 climate is closest to its 2011 to 2025 climate
Twins are stations, not cities. A twin is one of the three stations at least 100 km away whose earlier climate is closest to this station's recent one, so a close match does not mean the two places look alike in other ways. A station move or a gap in a record can change that station's averages. The list describes past climate; it is not a forecast and does not say what caused any change. How twins are found, and a search for any station.
Download the Data
Data for Mt Diablo Junction standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Mt Diablo Junction 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.