Weather in Bryn Mawr, Pennsylvania
Roses open along the stoops. Day 59 of spring. Read this microseason across nine climate regions →
- TodayMay 17Overcast—89°64°
- MondayMay 18Drizzle—95°67°
- TuesdayMay 19Light Drizzle—91°67°
- WednesdayMay 20Showers71%89°62°
- ThursdayMay 21Overcast36%74°53°
- FridayMay 22Drizzle30%62°49°
- SaturdayMay 23Light Drizzle36%56°49°
- PM 2.5
- 11.8 μg/m³
- PM 10
- 12.0 μg/m³
- NO₂
- 10.4 μg/m³
- Ozone
- 99.0 μg/m³
- UV Index
- 0.0 Low
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 9:49 AM
- Moonset
- 12:37 AM
- In sign
- ♊︎ Gemini
Roses open along the stoops
Bryn Mawr at a glance
- Today vs. normal: 4°F below the seasonal normal for this latitude
- Last frost: April 16 (climatological average for this latitude)
- Microseason: 28 of 72, May 16–20
- Planting window: Direct sow okra, melons, and southern peas. Thin carrot rows.
Right now in the garden
Warm-season window is open
As of May 17, the last spring frost has passed for most years. Transplant tomatoes, peppers, eggplants, basil, and cucurbits (cucumbers, squash, melons) now. Direct-sow beans and corn into warm soil.
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
Bryn Mawr's warmest month is July (~80°F mean) and its coldest is January (~35°F). Rainfall peaks in August (5.0 inches) and bottoms out in February (3.3 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 35° | 3.6″ | 7 |
| February | 37° | 3.3″ | 6 |
| March | 45° | 4.5″ | 7 |
| April | 56° | 4.0″ | 7 |
| May | 66° | 4.1″ | 8 |
| June | 75° | 4.8″ | 8 |
| July | 80° | 4.8″ | 7 |
| August | 78° | 5.0″ | 7 |
| September | 72° | 4.9″ | 6 |
| October | 60° | 4.2″ | 6 |
| November | 49° | 3.4″ | 6 |
| December | 40° | 4.3″ | 7 |
Regional context
Bryn Mawr 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: Philadelphia, PA, Pittsburgh, PA, Allentown, PA, Harrisburg, PA, Lancaster, PA.
Frequently asked
- When does it freeze in Bryn Mawr?
- Bryn Mawr's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Bryn Mawr?
- August is the wettest month with about 5.0 inches of rain on average; the city receives roughly 51 inches annually.
- What is the warmest month in Bryn Mawr?
- July is typically warmest, averaging about 80°F.
- What is the coldest month in Bryn Mawr?
- January is typically coldest, averaging about 35°F.
- When can I start a vegetable garden in Bryn Mawr?
- 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 Bryn Mawr get?
- Bryn Mawr averages about 82 rainy days per year.
- What hardiness zone is Bryn Mawr?
- Bryn Mawr'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
Bryn Mawr, Pennsylvania sits in a warm-summer humid continental climate zone. January means hover near 35°F while July averages 80°F — a 46°F seasonal swing.
Across the year, Bryn Mawr receives about 51 inches of precipitation spread over roughly 82 rainy days.
The rhythm of the year is set by latitude (40.0°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.