Boulder Hill, Illinois Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
Boulder Hill weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Mostly Clear——86°57°—
- FridayJun 5Showers46%0.61″77°66°-9°
- SaturdayJun 6Drizzle59%—82°68°+5°
- SundayJun 7Showers17%—80°68°-2°
- MondayJun 8Showers55%0.06″72°67°-8°
- TuesdayJun 9Light Showers35%—85°69°+13°
- WednesdayJun 10Thunderstorm23%—85°71°0°
Ozone at AQI 100 — peak already passed at 1 PM under clear skies. AQI up 34 in the last 6 hours — air quality is degrading. Levels should ease through evening.
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 100 — peak already passed at 1 PM under clear skies. Levels should ease through evening.
- Present
- AQI 100
- UV peak
- 3.6 at earlier today
- Sky at peak
- clear
- Projected peak
- AQI 100
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
- 4:28 AM
- Moonset
- 1:50 PM
- In sign
- ♒︎ Aquarius
Fireflies rise from the lawn
Boulder Hill at a glance
- Today vs. normal: 13°F above the seasonal normal for this latitude
- Last frost: April 26 (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 — Boulder Hill
SPC has placed Boulder Hill in the Marginal Risk category for severe thunderstorms tomorrow.
- TODAYNONENo severe risk
- TOMORROWMRGLMarginal Risk
- DAY 3TSTMGeneral Thunderstorms
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 | 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
Boulder Hill's warmest month is July (~74°F mean) and its coldest is January (~23°F). Rainfall peaks in May (4.9 inches) and bottoms out in February (1.8 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 23° | 1.9″ | 5 |
| February | 27° | 1.8″ | 4 |
| March | 38° | 2.4″ | 6 |
| April | 50° | 4.0″ | 8 |
| May | 61° | 4.9″ | 8 |
| June | 70° | 4.5″ | 8 |
| July | 74° | 4.2″ | 7 |
| August | 73° | 3.9″ | 7 |
| September | 66° | 3.4″ | 6 |
| October | 53° | 3.7″ | 6 |
| November | 40° | 2.7″ | 5 |
| December | 29° | 2.2″ | 5 |
Regional context
Boulder Hill 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: Chicago, IL, Rockford, IL, Round Lake Beach, IL, Aurora, IL, Naperville, IL.
Frequently asked
- When does it freeze in Boulder Hill?
- Boulder Hill's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Boulder Hill?
- May is the wettest month with about 4.9 inches of rain on average; the city receives roughly 39 inches annually.
- What is the warmest month in Boulder Hill?
- July is typically warmest, averaging about 74°F.
- What is the coldest month in Boulder Hill?
- January is typically coldest, averaging about 23°F.
- When can I start a vegetable garden in Boulder Hill?
- 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 Boulder Hill get?
- Boulder Hill averages about 74 rainy days per year.
- What hardiness zone is Boulder Hill?
- Boulder Hill'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
Boulder Hill, Illinois sits in a warm-summer humid continental climate zone. January means hover near 23°F while July averages 74°F — a 51°F seasonal swing.
Across the year, Boulder Hill receives about 39 inches of precipitation spread over roughly 74 rainy days.
The rhythm of the year is set by latitude (41.7°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.