Adelphi climate — normals and trends
Adelphi (United States) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 13.4 °C and it receives 1,038 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 (25.4 °C on average) and the coldest is January (1.1 °C). Rainfall peaks in July.
Adelphi averages 77 frost days, 53 hot days (≥ 30 °C) and 116 rainy days per year.
Adelphi has warmed by +1.7 °C between 1940 and 2025, or +0.20 °C per decade. This trend is statistically significant.
The number of frost days there went from about 85 to 69 per year over the period.
The hottest day of the period reached 40.3 °C (on 16 July 1988) and the coldest -22.1 °C (on 11 February 1979).
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
AdelphiMaryland
- coords
- 39.00°, -76.97°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
13.4°C
Average daily high
18.4°C
Average daily low
8.7°C
Annual rainfall
1,038mm
Sunshine / day
9.0h
Mean relative humidity
67%
Average peak wind
15.8km/h
Seasonal range
24.3°C
Frost days (< 0 °C)
77 d/yr
Hot days (≥ 30 °C)
53 d/yr
Rainy days (≥ 1 mm)
116 d/yr
Annual snowfall
44.1 cm
Average feels-like high
17.4 °C
Average feels-like low
6.7 °C
Average peak gust
35.8 km/h
Tropical nights (≥ 20 °C)
55 d/yr
Solar radiation
15.1 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.7 °C
since 1940
+0.2 °C per decade · r² = 0.42 · 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
40.3 °C
16 July 1988
Coldest day
-22.1 °C
11 February 1979
Wettest day
153 mm
14 September 1966
Windiest day
51.9 km/h
1 December 1974
Strongest gust
115.6 km/h
19 September 2003
Hottest feels-like
46.2 °C
22 July 2011
Coldest feels-like
-28.5 °C
19 January 1994
Snowiest day
40.8 cm
20 March 1958
Sunniest day
14.2 h
4 July 2025
Normals computed over complete calendar years 1940–2025.
A specific year
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Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 3.3 °C | -2.0 °C | 53 mm | -26 mm |
| Feb | 7.5 °C | +0.3 °C | 86 mm | +11 mm |
| Mar | 16.6 °C | +4.4 °C | 57 mm | -38 mm |
| Apr | 20.3 °C | +1.9 °C | 75 mm | -11 mm |
| May | 23.3 °C | -0.3 °C | 193 mm | +97 mm |
| Jun | 29.5 °C | +1.1 °C | 138 mm | +52 mm |
| Jul | 31.2 °C | +0.6 °C | 246 mm | +147 mm |
| Aug | 27.3 °C | -2.1 °C | 23 mm | -66 mm |
| Sep | 26.1 °C | +0.4 °C | 82 mm | -8 mm |
| Oct | 19.7 °C | +0.1 °C | 56 mm | -22 mm |
| Nov | 13.8 °C | +0.6 °C | 39 mm | -42 mm |
| Dec | 6.1 °C | -1.3 °C | 54 mm | -31 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 Adelphi?
Adelphi has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 13.4 °C and it receives 1,038 mm of precipitation per year.
What is the hottest day ever recorded in Adelphi?
The hottest day measured in Adelphi between 1940 and 2025 was 16 July 1988, reaching 40.3 °C.
What is the coldest day in Adelphi?
The coldest day measured in Adelphi between 1940 and 2025 was 11 February 1979, at -22.1 °C.
Does it snow in Adelphi?
Yes. Adelphi gets on average 44.1 cm of snow per year and has around 77 frost days.
Has the climate of Adelphi warmed?
Yes: Adelphi warmed by +1.7 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Adelphi?
The wettest day measured in Adelphi between 1940 and 2025 was 14 September 1966, with 153 mm of rain in 24 hours.
What was the windiest day in Adelphi?
The windiest day measured in Adelphi between 1940 and 2025 was 1 December 1974, with winds reaching 51.9 km/h.
What is the warmest month in Adelphi?
The warmest month in Adelphi is July (25.4 °C on average); the coldest is January (1.1 °C).
How much does it rain in Adelphi?
Adelphi receives on average 1,038 mm of precipitation per year, spread over about 116 rainy days.
Is it sunny in Adelphi?
Adelphi 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 Adelphi?
The heaviest 24-hour snowfall measured in Adelphi between 1940 and 2025 was 20 March 1958, with 40.8 cm.
Are there tropical nights in Adelphi?
Yes: Adelphi has on average 55 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Adelphi?
In Adelphi, between 1940 and 2025, the highest apparent temperature reached 46.2 °C on 22 July 2011, and the lowest was -28.5 °C on 19 January 1994.
Compare Adelphi with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Adelphi