Record envelope, standing records and threshold days for Alpharetta 4 SSW (USC00090219), Georgia, United States, with 111 years of record.
Key Facts for Alpharetta 4 SSW
Alpharetta 4 SSW (USC00090219) is a weather station in Georgia, United States at 34.10 latitude and -84.35 longitude, 347 m (1,138 ft) above sea level.
The station reports from 1901 to 2011, 111 years of record.
1,464 records set at Alpharetta 4 SSW still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Alpharetta 4 SSW set a daily record precipitation of 24.9 mm (1.0 in) on 23 June 2011.
About the Station
Location: Georgia, United States, 34.10 latitude, -84.35 longitude.
Elevation: 347 m (1,138 ft).
Period of record: 1901 to 2011, 111 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 Alpharetta 4 SSW. 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 Alpharetta 4 SSW, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
23.9 C (75.0 F)
-23.3 C (-9.9 F)
n/a
n/a
Feb
26.7 C (80.1 F)
-17.2 C (1.0 F)
n/a
n/a
Mar
31.1 C (88.0 F)
-14.4 C (6.1 F)
n/a
n/a
Apr
32.8 C (91.0 F)
-4.4 C (24.1 F)
n/a
n/a
May
35.0 C (95.0 F)
-0.6 C (30.9 F)
n/a
n/a
Jun
38.3 C (100.9 F)
4.4 C (39.9 F)
n/a
n/a
Jul
38.9 C (102.0 F)
8.9 C (48.0 F)
n/a
n/a
Aug
38.3 C (100.9 F)
10.0 C (50.0 F)
n/a
n/a
Sep
36.7 C (98.1 F)
-2.2 C (28.0 F)
n/a
n/a
Oct
31.1 C (88.0 F)
-3.9 C (25.0 F)
n/a
n/a
Nov
28.9 C (84.0 F)
-12.2 C (10.0 F)
n/a
n/a
Dec
24.4 C (75.9 F)
-18.3 C (-0.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at Alpharetta 4 SSW still stand. 1967 holds the most, with 60.
Standing records at Alpharetta 4 SSW by the year they were set
Year set
Standing records
1901
13
1902
49
1903
49
1904
5
1957
32
1958
25
1959
33
1960
48
1961
38
1962
47
1963
43
1964
28
1965
25
1966
22
1967
60
1968
39
1969
37
1970
33
1971
36
1972
21
1973
23
1974
35
1975
22
1976
28
1977
48
1978
21
1979
27
1980
33
1981
18
1982
29
1983
27
1984
33
1985
36
1986
37
1987
18
1988
26
1989
38
1990
46
1991
39
1992
19
1993
23
1994
17
1995
3
2007
37
2008
23
2009
17
2010
47
2011
11
All-Time Record Progression
3 new records
3 all-time records were set at Alpharetta 4 SSW between 21 January 1985 and 22 July 1986. Each dot is a new record.
When Alpharetta 4 SSW set new all-time records
Date
Kind
Detail
1985-01-21
Record low maximum temperature
Record low maximum temperature -11.1 C (12.0 F)
1985-01-21
Record low minimum temperature
Record low minimum temperature -23.3 C (-9.9 F)
1986-07-22
Record high maximum temperature
Record high maximum temperature 38.9 C (102.0 F)
Wettest Day of Each Month
Dec: 136.7 mm (5.4 in)
The wettest day on record for each calendar month at Alpharetta 4 SSW. The most was 136.7 mm (5.4 in) on 12 December 1961.
Record daily precipitation for each month at Alpharetta 4 SSW
Month
Record daily precipitation (mm)
Date
Jan
119.6 mm (4.7 in)
11 January 1972
Feb
121.9 mm (4.8 in)
3 February 1982
Mar
132.3 mm (5.2 in)
15 March 1990
Apr
80.5 mm (3.2 in)
29 April 1963
May
83.8 mm (3.3 in)
14 May 1972
Jun
98.6 mm (3.9 in)
16 June 2010
Jul
83.8 mm (3.3 in)
23 July 1970
Aug
80.0 mm (3.1 in)
22 August 1992
Sep
86.6 mm (3.4 in)
29 September 1963
Oct
97.8 mm (3.9 in)
1 October 1965
Nov
111.3 mm (4.4 in)
11 November 2009
Dec
136.7 mm (5.4 in)
12 December 1961
Period of Record Coverage
1901 to 2011
Complete yearUnder 90 percent of days
48 years of record at Alpharetta 4 SSW, 1901 to 2011. 11 years have data for under 90 percent of days and are left out of rankings: 1901, 1904, 1957, 1974, 1981, 1990, 1993, 1994 and others.
Cooler than the station meanWarmer than the station mean
One stripe for each of 34 complete years at Alpharetta 4 SSW, 1902 to 2010. Blue stripes are years cooler than the station's own mean of 14.5 C (58.2 F); red stripes are warmer. The coolest year was 1968, at 13.2 C (55.8 F), and the warmest was 1986, at 15.9 C (60.5 F). The strongest colour marks a difference of 1.4 C (2.5 F).
Annual mean temperature at Alpharetta 4 SSW as warming stripes, 1902 to 2010
Year
Annual mean temperature
Difference from the station mean
1902
15.6 C
+1.11 C
1958
14.8 C
+0.22 C
1959
15.7 C
+1.15 C
1960
14.3 C
-0.27 C
1961
14.6 C
+0.03 C
1962
14.8 C
+0.28 C
1964
14.6 C
+0.03 C
1965
15.0 C
+0.46 C
1966
14.0 C
-0.49 C
1967
13.7 C
-0.85 C
1968
13.2 C
-1.33 C
1969
13.5 C
-1.08 C
1970
14.1 C
-0.41 C
1971
14.3 C
-0.20 C
1972
14.2 C
-0.33 C
1973
14.7 C
+0.17 C
1975
14.7 C
+0.19 C
1976
13.6 C
-0.93 C
1977
14.4 C
-0.16 C
1978
14.1 C
-0.43 C
1979
13.9 C
-0.60 C
1980
14.3 C
-0.19 C
1982
14.6 C
+0.03 C
1983
13.9 C
-0.68 C
1984
14.5 C
-0.02 C
1985
14.7 C
+0.15 C
1986
15.9 C
+1.33 C
1987
15.1 C
+0.52 C
1988
14.9 C
+0.38 C
1991
15.4 C
+0.85 C
1992
14.6 C
+0.06 C
2008
14.9 C
+0.34 C
2009
14.9 C
+0.41 C
2010
14.9 C
+0.32 C
The fitted trend in annual mean temperature here over 1902 to 2010 is -0.01 C (-0.13 to 0.11) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: -0.02 F (-0.23 to 0.19) per decade. The slope is a straight line fitted to 34 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at Alpharetta 4 SSW
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
-0.01 C (-0.13 to 0.11) per decade
-0.02 F (-0.23 to 0.19) per decade
1902 to 2010
34
Not clearly different from zero
Mean daily maximum
-0.09 C (-0.19 to 0.00) per decade
-0.17 F (-0.34 to 0.00) per decade
1902 to 2010
34
Not clearly different from zero
Mean daily minimum
0.1 C (-0.1 to 0.2) per decade
0.1 F (-0.2 to 0.4) per decade
1902 to 2010
34
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
1901 to 2011
Yearly extremes at Alpharetta 4 SSW: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
38.9 C (102.0 F)
1986
35.0 C (95.0 F)
48
Coldest night (TNn)
-23.3 C (-9.9 F)
1985
-13.3 C (8.1 F)
48
Wettest day (Rx1day)
136.7 mm (5.4 in)
1961
73.3 mm (2.9 in)
48
Wettest five days (Rx5day)
251.8 mm (9.9 in)
2009
117.3 mm (4.6 in)
48
Longest dry spell (CDD)
33 days
1970
20 days
48
Hottest day (TXx)
The hottest day of the year at Alpharetta 4 SSW, 1901 to 2011. The record is 38.9 C (102.0 F) in 1986, marked on the chart; the median year is 35.0 C (95.0 F).
Hottest day (TXx) at Alpharetta 4 SSW by year
Year
Hottest day (TXx)
1901
28.9 C (84.0 F)
1902
37.2 C (99.0 F)
1903
35.0 C (95.0 F)
1904
22.2 C (72.0 F)
1957
37.2 C (99.0 F)
1958
36.1 C (97.0 F)
1959
36.7 C (98.1 F)
1960
37.2 C (99.0 F)
1961
34.4 C (93.9 F)
1962
36.1 C (97.0 F)
1963
35.0 C (95.0 F)
1964
36.7 C (98.1 F)
1965
33.9 C (93.0 F)
1966
36.7 C (98.1 F)
1967
32.8 C (91.0 F)
1968
36.7 C (98.1 F)
1969
38.3 C (100.9 F)
1970
36.7 C (98.1 F)
1971
34.4 C (93.9 F)
1972
34.4 C (93.9 F)
1973
33.3 C (91.9 F)
1974
32.8 C (91.0 F)
1975
33.9 C (93.0 F)
1976
34.4 C (93.9 F)
1977
37.8 C (100.0 F)
1978
35.6 C (96.1 F)
1979
33.9 C (93.0 F)
1980
37.8 C (100.0 F)
1981
35.0 C (95.0 F)
1982
32.2 C (90.0 F)
1983
37.8 C (100.0 F)
1984
33.9 C (93.0 F)
1985
34.4 C (93.9 F)
1986
38.9 C (102.0 F)
1987
35.6 C (96.1 F)
1988
36.7 C (98.1 F)
1989
33.9 C (93.0 F)
1990
37.8 C (100.0 F)
1991
32.8 C (91.0 F)
1992
33.9 C (93.0 F)
1993
36.7 C (98.1 F)
1994
32.2 C (90.0 F)
1995
22.8 C (73.0 F)
2007
38.3 C (100.9 F)
2008
36.1 C (97.0 F)
2009
34.4 C (93.9 F)
2010
35.6 C (96.1 F)
2011
35.0 C (95.0 F)
Coldest night (TNn)
The coldest night of the year at Alpharetta 4 SSW, 1901 to 2011. The record is -23.3 C (-9.9 F) in 1985, marked on the chart; the median year is -13.3 C (8.1 F).
Coldest night (TNn) at Alpharetta 4 SSW by year
Year
Coldest night (TNn)
1901
-15.0 C (5.0 F)
1902
-10.6 C (12.9 F)
1903
-11.1 C (12.0 F)
1904
-10.0 C (14.0 F)
1957
-13.9 C (7.0 F)
1958
-17.2 C (1.0 F)
1959
-13.9 C (7.0 F)
1960
-14.4 C (6.1 F)
1961
-14.4 C (6.1 F)
1962
-18.3 C (-0.9 F)
1963
-21.1 C (-6.0 F)
1964
-12.8 C (9.0 F)
1965
-12.8 C (9.0 F)
1966
-20.6 C (-5.1 F)
1967
-15.0 C (5.0 F)
1968
-12.2 C (10.0 F)
1969
-14.4 C (6.1 F)
1970
-17.8 C (0.0 F)
1971
-14.4 C (6.1 F)
1972
-16.1 C (3.0 F)
1973
-12.2 C (10.0 F)
1974
-9.4 C (15.1 F)
1975
-11.7 C (10.9 F)
1976
-13.3 C (8.1 F)
1977
-18.9 C (-2.0 F)
1978
-13.3 C (8.1 F)
1979
-12.8 C (9.0 F)
1980
-13.3 C (8.1 F)
1981
-13.3 C (8.1 F)
1982
-18.9 C (-2.0 F)
1983
-18.3 C (-0.9 F)
1984
-13.3 C (8.1 F)
1985
-23.3 C (-9.9 F)
1986
-15.0 C (5.0 F)
1987
-9.4 C (15.1 F)
1988
-12.2 C (10.0 F)
1989
-13.3 C (8.1 F)
1990
-12.2 C (10.0 F)
1991
-11.7 C (10.9 F)
1992
-10.0 C (14.0 F)
1993
-11.7 C (10.9 F)
1994
-16.7 C (1.9 F)
1995
-11.7 C (10.9 F)
2007
-8.3 C (17.1 F)
2008
-10.6 C (12.9 F)
2009
-12.8 C (9.0 F)
2010
-12.2 C (10.0 F)
2011
-10.0 C (14.0 F)
Wettest day (Rx1day)
The wettest day of the year at Alpharetta 4 SSW, 1901 to 2011. The record is 136.7 mm (5.4 in) in 1961, marked on the chart; the median year is 73.3 mm (2.9 in).
Wettest day (Rx1day) at Alpharetta 4 SSW by year
Year
Wettest day (Rx1day)
1901
44.5 mm (1.8 in)
1902
86.4 mm (3.4 in)
1903
87.9 mm (3.5 in)
1904
29.0 mm (1.1 in)
1957
47.0 mm (1.9 in)
1958
70.4 mm (2.8 in)
1959
71.1 mm (2.8 in)
1960
76.7 mm (3.0 in)
1961
136.7 mm (5.4 in)
1962
94.5 mm (3.7 in)
1963
86.6 mm (3.4 in)
1964
118.1 mm (4.6 in)
1965
97.8 mm (3.9 in)
1966
97.0 mm (3.8 in)
1967
66.5 mm (2.6 in)
1968
76.2 mm (3.0 in)
1969
71.9 mm (2.8 in)
1970
98.8 mm (3.9 in)
1971
56.4 mm (2.2 in)
1972
119.6 mm (4.7 in)
1973
65.8 mm (2.6 in)
1974
52.6 mm (2.1 in)
1975
57.7 mm (2.3 in)
1976
83.8 mm (3.3 in)
1977
114.0 mm (4.5 in)
1978
60.2 mm (2.4 in)
1979
80.0 mm (3.1 in)
1980
77.5 mm (3.1 in)
1981
46.5 mm (1.8 in)
1982
121.9 mm (4.8 in)
1983
58.7 mm (2.3 in)
1984
53.3 mm (2.1 in)
1985
64.5 mm (2.5 in)
1986
60.5 mm (2.4 in)
1987
60.2 mm (2.4 in)
1988
74.7 mm (2.9 in)
1989
76.5 mm (3.0 in)
1990
132.3 mm (5.2 in)
1991
78.7 mm (3.1 in)
1992
80.0 mm (3.1 in)
1993
50.8 mm (2.0 in)
1994
53.8 mm (2.1 in)
1995
50.8 mm (2.0 in)
2007
47.0 mm (1.9 in)
2008
67.1 mm (2.6 in)
2009
111.3 mm (4.4 in)
2010
98.6 mm (3.9 in)
2011
54.9 mm (2.2 in)
Wettest five days (Rx5day)
The wettest five days of the year at Alpharetta 4 SSW, 1901 to 2011. The record is 251.8 mm (9.9 in) in 2009, marked on the chart; the median year is 117.3 mm (4.6 in).
Wettest five days (Rx5day) at Alpharetta 4 SSW by year
Year
Wettest five days (Rx5day)
1901
97.5 mm (3.8 in)
1902
116.1 mm (4.6 in)
1903
161.8 mm (6.4 in)
1904
54.8 mm (2.2 in)
1957
70.4 mm (2.8 in)
1958
91.4 mm (3.6 in)
1959
124.8 mm (4.9 in)
1960
105.1 mm (4.1 in)
1961
243.7 mm (9.6 in)
1962
139.3 mm (5.5 in)
1963
158.3 mm (6.2 in)
1964
118.1 mm (4.6 in)
1965
103.1 mm (4.1 in)
1966
163.0 mm (6.4 in)
1967
148.6 mm (5.9 in)
1968
82.8 mm (3.3 in)
1969
125.8 mm (5.0 in)
1970
143.3 mm (5.6 in)
1971
100.1 mm (3.9 in)
1972
179.5 mm (7.1 in)
1973
109.8 mm (4.3 in)
1974
84.1 mm (3.3 in)
1975
102.4 mm (4.0 in)
1976
130.8 mm (5.1 in)
1977
143.8 mm (5.7 in)
1978
119.6 mm (4.7 in)
1979
133.8 mm (5.3 in)
1980
184.0 mm (7.2 in)
1981
69.1 mm (2.7 in)
1982
145.5 mm (5.7 in)
1983
148.1 mm (5.8 in)
1984
137.8 mm (5.4 in)
1985
84.7 mm (3.3 in)
1986
105.9 mm (4.2 in)
1987
111.0 mm (4.4 in)
1988
87.7 mm (3.5 in)
1989
204.1 mm (8.0 in)
1990
183.9 mm (7.2 in)
1991
116.8 mm (4.6 in)
1992
100.8 mm (4.0 in)
1993
87.4 mm (3.4 in)
1994
106.6 mm (4.2 in)
1995
117.8 mm (4.6 in)
2007
52.9 mm (2.1 in)
2008
174.0 mm (6.9 in)
2009
251.8 mm (9.9 in)
2010
102.4 mm (4.0 in)
2011
94.5 mm (3.7 in)
Longest dry spell (CDD)
The longest dry spell of the year at Alpharetta 4 SSW, 1901 to 2011. The record is 33 days in 1970, marked on the chart; the median year is 20 days.
Longest dry spell (CDD) at Alpharetta 4 SSW by year
Year
Longest dry spell (CDD)
1901
18 days
1902
20 days
1903
28 days
1904
8 days
1957
20 days
1958
27 days
1959
16 days
1960
16 days
1961
30 days
1962
13 days
1963
32 days
1964
18 days
1965
19 days
1966
15 days
1967
22 days
1968
20 days
1969
17 days
1970
33 days
1971
16 days
1972
14 days
1973
26 days
1974
18 days
1975
19 days
1976
23 days
1977
23 days
1978
24 days
1979
16 days
1980
25 days
1981
23 days
1982
19 days
1983
18 days
1984
31 days
1985
23 days
1986
19 days
1987
19 days
1988
17 days
1989
33 days
1990
18 days
1991
22 days
1992
21 days
1993
27 days
1994
12 days
1995
9 days
2007
28 days
2008
21 days
2009
12 days
2010
23 days
2011
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
34 years with a frost
Across 34 years with a frost, the median last spring frost at Alpharetta 4 SSW falls on 11 April and the median first autumn frost on 29 October, which leaves a median of 200 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 Alpharetta 4 SSW
Measure
Median, all years
Earliest period
Recent period (1961 to 2010)
Recent against earliest
Fitted trend
Last spring frost
11 April
n/a
11 April
n/a
-1.2 days per decade
First autumn frost
29 October
n/a
1 November
n/a
+1.9 days per decade
Growing days
200 days
n/a
201 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
40 years, 1902 to 2010
A day with at least 77.3 mm (3.0 in) of rain is expected about once in 2 years. A day with at least 160.6 mm (6.3 in) of rain is expected about once in 100 years.
Rainfall return levels at Alpharetta 4 SSW: the daily rain expected about once in a given number of years
Expected about once in
A day with at least
Note
2 years
77.3 mm (3.0 in)
5 years
99.0 mm (3.9 in)
10 years
113.6 mm (4.5 in)
25 years
132.3 mm (5.2 in)
50 years
146.4 mm (5.8 in)
Longer than the 40 years of record
100 years
160.6 mm (6.3 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 1902 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: 136.7 mm (5.4 in) in 1961; 132.3 mm (5.2 in) in 1990; 121.9 mm (4.8 in) in 1982.
Download the Data
Data for Alpharetta 4 SSW standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Alpharetta 4 SSW 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.