Weather in Portland, Maine
Roses open along the stoops. Day 59 of spring. Read this microseason across nine climate regions →
- TodayMay 16Overcast—73°50°
- SundayMay 17Overcast27%78°56°
- MondayMay 18Overcast—65°50°
- TuesdayMay 19Overcast22%93°54°
- WednesdayMay 20Overcast45%91°63°
- ThursdayMay 21Overcast15%67°50°
- FridayMay 22Overcast—69°48°
- PM 2.5
- 7.1 μg/m³
- PM 10
- 8.1 μg/m³
- NO₂
- 5.8 μg/m³
- Ozone
- 95.0 μg/m³
- UV Index
- 0.0 Low
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 9:12 AM
- Moonset
- 12:30 AM
- In sign
- ♉︎ Taurus
Roses open along the stoops
Portland at a glance
- Today vs. normal: 12°F below the seasonal normal for this latitude
- Last frost: May 8 (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
Cool-season window is open
As of May 17, the cool-season window is open or about to open. Direct-sow peas, lettuce, spinach, radishes, and brassicas now. Hold off on warm-season crops until 1–2 weeks after the last spring frost (around May).
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | — | — |
| May | lettuce, peas, spinach, radishes | lettuce, peas, radishes |
| June | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | tomatoes, peppers, beans, squash, fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | — | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
July brings Portland's warmest temperatures at roughly 70°F mean, while January delivers the coldest at around 24°F. October sees peak rainfall with 5.3 inches, contrasting with July's drier 3.4 inches.
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 24° | 3.5″ | 7 |
| February | 26° | 3.5″ | 7 |
| March | 34° | 4.1″ | 7 |
| April | 45° | 4.4″ | 7 |
| May | 55° | 3.7″ | 7 |
| June | 64° | 4.2″ | 7 |
| July | 70° | 3.4″ | 7 |
| August | 69° | 3.6″ | 5 |
| September | 62° | 3.8″ | 5 |
| October | 50° | 5.3″ | 7 |
| November | 40° | 4.3″ | 7 |
| December | 30° | 4.5″ | 8 |
Regional context
Portland falls within the warm-summer humid continental climate region, sharing temperature ranges, seasonal patterns, and growing conditions with other nearby cities in this climate zone.
Similar climates: Lewiston, ME, Bangor, ME, South Portland, ME, Auburn, ME, Biddeford, ME.
Naturalist notes
Late May brings the first ruby-throated hummingbirds to Portland's gardens, their migration timed with the blooming of native honeysuckle.
Apple trees across the region typically reach full bloom by mid-May, marking the transition from spring's cool nights to the approaching warmth of early summer.
Frequently asked
- When does it freeze in Portland?
- Portland's last spring frost typically occurs around mid-May, while the first fall frost returns around mid-October.
- What is the rainy season in Portland?
- October receives the most rainfall with approximately 5.3 inches on average; the city sees roughly 48 inches total annually.
- What is the warmest month in Portland?
- July typically records the warmest temperatures, averaging about 70°F.
- What is the coldest month in Portland?
- January typically brings the coldest weather, averaging about 24°F.
- When can I start a vegetable garden in Portland?
- Cool-season crops like peas and lettuce can be planted around the last spring frost in mid-May; warm-season crops such as tomatoes and peppers should wait 1–2 weeks after.
- How many rainy days does Portland get?
- Portland experiences about 80 rainy days per year on average.
- What hardiness zone is Portland?
- Portland's USDA hardiness zone depends on its lowest average winter temperature; use the USDA's online lookup tool with the city ZIP code for the current zone designation.
Climate
Portland, Maine experiences a warm-summer humid continental climate. Winter brings January temperatures that hover near 24°F, while summer peaks in July with averages around 70°F — creating a 46°F seasonal swing.
Annual precipitation totals about 48 inches, falling across roughly 80 rainy days throughout the year.
Geography drives Portland's weather patterns through its latitude of 43.7°N, proximity to large water bodies, and elevation. These factors determine what grows in the region, when frost threatens, and how daily weather unfolds.