South Portland, Maine Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
South Portland weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——81°52°—
- FridayJun 5Overcast——84°58°+3°
- SaturdayJun 6Showers26%0.21″83°54°-1°
- SundayJun 7Light Showers72%0.09″73°55°-10°
- MondayJun 8Overcast24%—73°54°0°
- TuesdayJun 9Overcast——79°54°+6°
- WednesdayJun 10Overcast——79°60°0°
Ozone at AQI 61 now. AQI up 12 over the last 6 hours (gradual rise). With UV 7.0 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 57 by mid-afternoon.
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 61 now. With UV 7.0 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 57 by mid-afternoon.
- Present
- AQI 61
- UV peak
- 7.0 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 57
PM × Wind × Precip
PM2.5 at 7.1 µg/m³, PM10 at 8.8 µg/m³ — typical background levels with no transport signature.
- PM2.5/PM10
- 0.81
- Wind
- breezy
- 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).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 3:21 AM
- Moonset
- 12:27 PM
- In sign
- ♒︎ Aquarius
Fireflies rise from the lawn
South Portland at a glance
- Today vs. normal: 7°F above the seasonal normal for this latitude
- Last frost: May 8 (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 4, 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.
SPC Convective Outlook
Storm Prediction Center — South Portland
SPC has placed South Portland in the Marginal Risk category for severe thunderstorms day after tomorrow.
- TODAYNONENo severe risk
- TOMORROWNONENo severe risk
- DAY 3MRGLMarginal Risk
Isolated severe storms possible. Limited threat for hail or damaging wind.
Source: NOAA / NWS Storm Prediction Center categorical convective outlook. Outlooks are re-issued multiple times per day; this page reflects the most recent SPC polygons covering the city’s coordinates.
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
South Portland's warmest month is July (~70°F mean) and its coldest is January (~24°F). Rainfall peaks in October (5.3 inches) and bottoms out in July (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
South Portland 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: Portland, ME, Lewiston, ME, Bangor, ME, Auburn, ME, Biddeford, ME.
Frequently asked
- When does it freeze in South Portland?
- South Portland's last spring frost typically falls around mid-May, and the first fall frost arrives around mid-October.
- What is the rainy season in South Portland?
- October is the wettest month with about 5.3 inches of rain on average; the city receives roughly 48 inches annually.
- What is the warmest month in South Portland?
- July is typically warmest, averaging about 70°F.
- What is the coldest month in South Portland?
- January is typically coldest, averaging about 24°F.
- When can I start a vegetable garden in South Portland?
- Cool-season crops (peas, lettuce) can be sown around the last spring frost (mid-May); warm-season crops (tomatoes, peppers) wait until 1–2 weeks after.
- How many rainy days does South Portland get?
- South Portland averages about 80 rainy days per year.
- What hardiness zone is South Portland?
- South Portland'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
South Portland, Maine sits in a warm-summer humid continental climate zone. January means hover near 24°F while July averages 70°F — a 46°F seasonal swing.
Across the year, South Portland receives about 48 inches of precipitation spread over roughly 80 rainy days.
The rhythm of the year is set by latitude (43.6°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.