Round Lake Heights, Illinois Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
Round Lake Heights weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——86°55°—
- FridayJun 5Rain80%0.20″77°68°-9°
- SaturdayJun 6Showers51%0.12″83°63°+6°
- SundayJun 7Light Drizzle——76°58°-7°
- MondayJun 8Heavy Drizzle34%—81°61°+5°
- TuesdayJun 9Light Drizzle26%—81°67°0°
- WednesdayJun 10Heavy Drizzle19%0.01″82°69°+1°
PM2.5 at 12.5 µg/m³ (AQI 57) with a 0.92 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust. AQI down 18 over the last 6 hours — air quality is improving sharply.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
PM × Wind × Precip
PM2.5 at 12.5 µg/m³ (AQI 57) with a 0.92 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.92
- Wind
- calm
- 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).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 4:30 AM
- Moonset
- 1:46 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Round Lake Heights at a glance
- Today vs. normal: 16°F below the seasonal normal for this latitude
- 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.
SPC Convective Outlook
Storm Prediction Center — Round Lake Heights
SPC has placed Round Lake Heights in the Marginal Risk category for severe thunderstorms tomorrow.
- TODAYTSTMGeneral Thunderstorms
- TOMORROWMRGLMarginal 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
Round Lake Heights's warmest month is July (~73°F mean) and its coldest is January (~22°F). Rainfall peaks in May (4.4 inches) and bottoms out in February (1.9 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 22° | 2.1″ | 6 |
| February | 26° | 1.9″ | 4 |
| March | 36° | 2.6″ | 5 |
| April | 47° | 4.1″ | 7 |
| May | 58° | 4.4″ | 7 |
| June | 68° | 4.2″ | 6 |
| July | 73° | 3.9″ | 6 |
| August | 71° | 3.3″ | 6 |
| September | 64° | 3.4″ | 5 |
| October | 52° | 3.0″ | 5 |
| November | 39° | 2.5″ | 6 |
| December | 28° | 2.3″ | 4 |
Regional context
Round Lake Heights 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 Round Lake Heights?
- Round Lake Heights's last spring frost typically falls around mid-May, and the first fall frost arrives around mid-October.
- What is the rainy season in Round Lake Heights?
- May is the wettest month with about 4.4 inches of rain on average; the city receives roughly 38 inches annually.
- What is the warmest month in Round Lake Heights?
- July is typically warmest, averaging about 73°F.
- What is the coldest month in Round Lake Heights?
- January is typically coldest, averaging about 22°F.
- When can I start a vegetable garden in Round Lake Heights?
- 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 Round Lake Heights get?
- Round Lake Heights averages about 67 rainy days per year.
- What hardiness zone is Round Lake Heights?
- Round Lake Heights'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
Round Lake Heights, Illinois sits in a warm-summer humid continental climate zone. January means hover near 22°F while July averages 73°F — a 51°F seasonal swing.
Across the year, Round Lake Heights receives about 38 inches of precipitation spread over roughly 67 rainy days.
The rhythm of the year is set by latitude (42.4°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.