Waltham, Massachusetts Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
Waltham weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Clear——86°52°—
- ThursdayJun 4Overcast——88°59°+2°
- FridayJun 5Overcast——88°59°0°
- SaturdayJun 6Showers23%0.16″90°66°+2°
- SundayJun 7Drizzle74%0.01″83°56°-7°
- MondayJun 8Overcast30%—76°54°-7°
- TuesdayJun 9Overcast13%—81°54°+5°
Ozone at AQI 44 now. AQI up 9 over the last 6 hours (gradual rise). With UV 0.0 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 11 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 44 now. With UV 0.0 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 11 by mid-afternoon.
- Present
- AQI 44
- UV peak
- 0.0 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 11
PM × Wind × Precip
PM2.5 at 6.6 µg/m³, PM10 at 6.9 µg/m³ — typical background levels with no transport signature.
- PM2.5/PM10
- 0.96
- 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
- 3:20 AM
- Moonset
- 12:35 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Waltham at a glance
- Today vs. normal: 72°F — typical for the season
- Last frost: April 30 (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.