Waltham, Massachusetts Weather
Cicadas claim the afternoon. Day 15 of summer. Read this microseason across nine climate regions →
Waltham weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 5Overcast12%—86°71°—
- MondayJul 6Drizzle65%0.04″79°64°-7°
- TuesdayJul 7Showers73%0.98″63°60°-16°
- WednesdayJul 8Overcast26%—80°57°+17°
- ThursdayJul 9Overcast11%—90°63°+10°
- FridayJul 10Overcast36%—85°68°-5°
- SaturdayJul 11Overcast17%—78°60°-7°
AQI 54 (Moderate), driven by PM2.5. AQI up 10 over the last 6 hours (gradual rise). PM2.5 at 23.6 µg/m³ (AQI 78) with a 0.91 fine-to-coarse ratio and 5 mph wind — combustion smoke trapped in calm air, not road dust.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion during the projected peak around 7 PM.
What's driving it
Ozone × UV × Sky
Ozone at AQI 35. Overcast through the UV peak window (cloud cover ~96%) — afternoon ozone should stay flat.
- Present
- AQI 35
- UV peak
- 5.0 at 1 PM
- Sky at peak
- overcast
- Projected peak
- AQI 12
PM × Wind × Precip
PM2.5 at 23.6 µg/m³ (AQI 78) with a 0.91 fine-to-coarse ratio and 5 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.91
- Wind
- light
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
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).
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
- Moonrise
- 11:03 PM
- Moonset
- 10:53 AM
- In sign
- ♓︎ Pisces
Cicadas claim the afternoon
Waltham at a glance
- Today vs. normal: 9°F above the seasonal normal for this latitude
- Last frost: April 30 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
ZIP codes: 02451, 02452, 02453
16-Day Forecast — Waltham
- Sun86°71°12%
- Mon79°64°65%
- Tue63°60°73%
- Wed80°57°26%
- Thu90°63°11%
- Fri85°68°36%
- Sat78°60°17%
- Sun72°61°13%
- Mon75°57°18%
- Tue86°58°19%
- Wed89°71°15%
- Thu85°63°18%
- Fri91°62°19%
- Sat95°66°17%
- Sun87°68°24%
- Mon81°71°28%
Forecast data from Open-Meteo (CC BY 4.0).
Live wind & temperature near Waltham
Right now in the garden
Peak growing season
As of July 5, 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 — Waltham
SPC includes Waltham in the general thunderstorm area tomorrow — no severe risk, but storms are possible.
- TODAYNONENo severe risk
- TOMORROWTSTMGeneral Thunderstorms
- DAY 3NONENo severe risk
Thunderstorms possible. Not severe, but capable of producing lightning and brief heavy rain.
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.
ZIP codes in Waltham
- 02453
- 02451
- 02452
- 02454
- 02455