Adelphi, Maryland Weather
Fireflies rise from the lawn. Day 76 of spring. Read this microseason across nine climate regions →
Adelphi weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Clear——82°53°—
- ThursdayJun 4Overcast——88°57°+6°
- FridayJun 5Overcast——91°62°+3°
- SaturdayJun 6Overcast12%—96°69°+5°
- SundayJun 7Light Showers34%0.04″84°67°-12°
- MondayJun 8Light Drizzle29%—78°60°-6°
- TuesdayJun 9Mostly Clear18%—83°55°+5°
Ozone at AQI 78 — peak already passed at 1 PM under clear skies. AQI up 5 over the last 6 hours (gradual rise). Levels should ease through evening.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 78 — peak already passed at 1 PM under clear skies. Levels should ease through evening.
- Present
- AQI 78
- UV peak
- 3.8 at earlier today
- Sky at peak
- clear
- Projected peak
- AQI 78
PM × Wind × Precip
PM2.5 at 5.4 µg/m³, PM10 at 7.1 µg/m³ — typical background levels with no transport signature.
- PM2.5/PM10
- 0.76
- Wind
- light
- Recent rain
- 0h in last 6h
- Pattern
- background
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
The higher the clouds, the finer the weather.
- Moonrise
- 2:54 AM
- Moonset
- 12:08 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Adelphi at a glance
- Today vs. normal: 6°F above the seasonal normal for this latitude
- Last frost: April 10 (climatological average for this latitude)
- Microseason: Jun 1–5
- Planting window: Harvest spring lettuce before it bolts. Sow heat-tolerant greens.
Right now in the garden
Peak growing season
As of June 3, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | lettuce, peas, spinach, radishes | — |
| May | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | — | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | fall brassicas, garlic (overwinter), carrots | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
Adelphi's warmest month is July (~80°F mean) and its coldest is January (~36°F). Rainfall peaks in July (4.6 inches) and bottoms out in February (2.8 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 36° | 3.0″ | 6 |
| February | 39° | 2.8″ | 5 |
| March | 46° | 4.0″ | 7 |
| April | 57° | 3.4″ | 7 |
| May | 67° | 4.3″ | 8 |
| June | 76° | 4.6″ | 8 |
| July | 80° | 4.6″ | 7 |
| August | 79° | 3.7″ | 7 |
| September | 72° | 4.1″ | 6 |
| October | 59° | 4.2″ | 5 |
| November | 49° | 3.2″ | 5 |
| December | 41° | 3.7″ | 7 |
Regional context
Adelphi sits within a warm-summer humid continental climate region — a cohort that shares similar temperature ranges, seasonal patterns, and growing conditions across nearby cities.
Similar climates: Baltimore, MD, Hagerstown, MD, Frederick, MD, Waldorf, MD, Columbia, MD.
Frequently asked
- When does it freeze in Adelphi?
- Adelphi's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Adelphi?
- July is the wettest month with about 4.6 inches of rain on average; the city receives roughly 46 inches annually.
- What is the warmest month in Adelphi?
- July is typically warmest, averaging about 80°F.
- What is the coldest month in Adelphi?
- January is typically coldest, averaging about 36°F.
- When can I start a vegetable garden in Adelphi?
- Cool-season crops (peas, lettuce) can be sown around the last spring frost (mid-April); warm-season crops (tomatoes, peppers) wait until 1–2 weeks after.
- How many rainy days does Adelphi get?
- Adelphi averages about 79 rainy days per year.
- What hardiness zone is Adelphi?
- Adelphi's USDA hardiness zone is determined by its lowest average winter temperature; check the USDA's online lookup with the city ZIP for the current zone designation.
Climate
Adelphi, Maryland sits in a warm-summer humid continental climate zone. January means hover near 36°F while July averages 80°F — a 44°F seasonal swing.
Across the year, Adelphi receives about 46 inches of precipitation spread over roughly 79 rainy days.
The rhythm of the year is set by latitude (39.0°N), proximity to large water bodies, and elevation — all of which shape what grows here, when frost is likely, and what the weather story looks like day to day.