Alpharetta climate — normals and trends
Alpharetta (United States) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 16.0 °C and it receives 1,221 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is July (25.6 °C on average) and the coldest is January (5.5 °C). Rainfall peaks in March.
Alpharetta averages 42 frost days, 61 hot days (≥ 30 °C) and 126 rainy days per year.
Alpharetta has warmed by +1.2 °C between 1940 and 2025, or +0.14 °C per decade. This trend is statistically significant.
The hottest day of the period reached 40.1 °C (on 30 June 2012) and the coldest -22.9 °C (on 21 January 1985).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
AlpharettaGeorgia
- coords
- 34.08°, -84.29°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
16.0°C
Average daily high
21.4°C
Average daily low
11.3°C
Annual rainfall
1,221mm
Sunshine / day
9.0h
Mean relative humidity
71%
Average peak wind
15.7km/h
Seasonal range
20.1°C
Frost days (< 0 °C)
42 d/yr
Hot days (≥ 30 °C)
61 d/yr
Rainy days (≥ 1 mm)
126 d/yr
Annual snowfall
5.9 cm
Average feels-like high
21.3 °C
Average feels-like low
10.0 °C
Average peak gust
34.7 km/h
Tropical nights (≥ 20 °C)
79 d/yr
Solar radiation
16.0 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.2 °C
since 1940
+0.1 °C per decade · r² = 0.26 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
40.1 °C
30 June 2012
Coldest day
-22.9 °C
21 January 1985
Wettest day
110 mm
25 September 1956
Windiest day
54.7 km/h
5 October 1995
Strongest gust
126.4 km/h
5 October 1995
Hottest feels-like
44.3 °C
30 June 2012
Coldest feels-like
-29.9 °C
21 January 1985
Snowiest day
21.4 cm
23 January 1940
Sunniest day
13.9 h
25 June 2024
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 8.7 °C | -2.0 °C | 75 mm | -41 mm |
| Feb | 15.8 °C | +2.8 °C | 120 mm | +4 mm |
| Mar | 20.1 °C | +3.0 °C | 84 mm | -44 mm |
| Apr | 23.9 °C | +2.1 °C | 130 mm | +24 mm |
| May | 24.9 °C | -1.0 °C | 189 mm | +96 mm |
| Jun | 29.6 °C | +0.2 °C | 130 mm | +37 mm |
| Jul | 32.4 °C | +1.8 °C | 105 mm | -3 mm |
| Aug | 28.4 °C | -1.9 °C | 125 mm | +31 mm |
| Sep | 28.7 °C | +1.3 °C | 32 mm | -56 mm |
| Oct | 22.5 °C | +0.2 °C | 53 mm | -24 mm |
| Nov | 19.0 °C | +2.4 °C | 44 mm | -49 mm |
| Dec | 13.9 °C | +1.8 °C | 39 mm | -69 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Alpharetta?
Alpharetta has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 16.0 °C and it receives 1,221 mm of precipitation per year.
What is the hottest day ever recorded in Alpharetta?
The hottest day measured in Alpharetta between 1940 and 2025 was 30 June 2012, reaching 40.1 °C.
What is the coldest day in Alpharetta?
The coldest day measured in Alpharetta between 1940 and 2025 was 21 January 1985, at -22.9 °C.
Does it snow in Alpharetta?
Yes. Alpharetta gets on average 5.9 cm of snow per year and has around 42 frost days.
Has the climate of Alpharetta warmed?
Yes: Alpharetta warmed by +1.2 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Alpharetta?
The wettest day measured in Alpharetta between 1940 and 2025 was 25 September 1956, with 110 mm of rain in 24 hours.
What was the windiest day in Alpharetta?
The windiest day measured in Alpharetta between 1940 and 2025 was 5 October 1995, with winds reaching 54.7 km/h.
What is the warmest month in Alpharetta?
The warmest month in Alpharetta is July (25.6 °C on average); the coldest is January (5.5 °C).
How much does it rain in Alpharetta?
Alpharetta receives on average 1,221 mm of precipitation per year, spread over about 126 rainy days.
Is it sunny in Alpharetta?
Alpharetta gets on average 9.0 hours of sunshine per day, roughly 3,285 hours per year over 1940-2025.
What is the biggest single-day snowfall in Alpharetta?
The heaviest 24-hour snowfall measured in Alpharetta between 1940 and 2025 was 23 January 1940, with 21.4 cm.
Are there tropical nights in Alpharetta?
Yes: Alpharetta has on average 79 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Alpharetta?
In Alpharetta, between 1940 and 2025, the highest apparent temperature reached 44.3 °C on 30 June 2012, and the lowest was -29.9 °C on 21 January 1985.
Compare Alpharetta with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Alpharetta