Round Lake Beach, Illinois Weather
Fireflies rise from the lawn. Day 76 of spring. Read this microseason across nine climate regions →
Round Lake Beach weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Overcast——81°47°—
- ThursdayJun 4Overcast——86°57°+5°
- FridayJun 5Drizzle67%0.04″77°67°-9°
- SaturdayJun 6Light Drizzle55%0.02″80°59°+3°
- SundayJun 7Foggy11%—75°56°-5°
- MondayJun 8Light Drizzle15%—78°57°+3°
- TuesdayJun 9Light Drizzle23%0.02″77°68°-1°
Ozone at AQI 56 now. AQI flat over the last 6 hours (within ±3 points). With UV 6.7 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 50 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 56 now. With UV 6.7 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 50 by mid-afternoon.
- Present
- AQI 56
- UV peak
- 6.7 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 50
PM × Wind × Precip
PM2.5 at 9.3 µg/m³ (AQI 51) with a 0.93 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.93
- 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).
The higher the clouds, the finer the weather.
- Moonrise
- 3:53 AM
- Moonset
- 12:41 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Round Lake Beach at a glance
- Today vs. normal: 8°F above 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 3, 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 Beach
SPC has placed Round Lake Beach 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
July brings Round Lake Beach's warmest temperatures (~73°F mean) while January delivers the coldest (~22°F). Precipitation follows its own calendar, peaking in May with 4.4 inches and reaching its lowest point in February at 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 Beach belongs to the warm-summer humid continental climate region. Cities throughout this zone experience similar temperature ranges, seasonal patterns, and growing conditions.
Similar climates: Chicago, IL, Rockford, IL, Aurora, IL, Naperville, IL, Joliet, IL.
Naturalist notes
Late May brings the return of ruby-throated hummingbirds to Round Lake Beach, their iridescent forms appearing at feeders and flowering trees as spring transitions toward summer.
Spring ephemeral wildflowers like bloodroot and trout lily bloom in early April, completing their life cycles before the forest canopy fully leafs out.
Frequently asked
- When does it freeze in Round Lake Beach?
- Round Lake Beach typically sees its last spring frost around mid-May, with the first fall frost returning around mid-October.
- What is the rainy season in Round Lake Beach?
- May ranks as the wettest month, averaging about 4.4 inches of rain, while the city receives roughly 38 inches annually.
- What is the warmest month in Round Lake Beach?
- July typically brings the warmest weather, averaging about 73°F.
- What is the coldest month in Round Lake Beach?
- January typically delivers the coldest temperatures, averaging about 22°F.
- When can I start a vegetable garden in Round Lake Beach?
- Cool-season crops like peas and lettuce can be planted around the last spring frost in mid-May, while warm-season crops such as tomatoes and peppers should wait 1–2 weeks after.
- How many rainy days does Round Lake Beach get?
- Round Lake Beach sees approximately 67 rainy days per year on average.
- What hardiness zone is Round Lake Beach?
- Round Lake Beach's USDA hardiness zone depends on its lowest average winter temperature; use the USDA's online lookup tool with the city ZIP for the current zone designation.
Climate
Round Lake Beach, Illinois experiences a warm-summer humid continental climate zone. Winter brings January temperatures that hover near 22°F, while summer sees July averages around 73°F — creating a 51°F seasonal swing.
Annual precipitation totals about 38 inches, falling across roughly 67 rainy days throughout the year.
Geography shapes the local weather patterns through latitude (42.4°N), proximity to large water bodies, and elevation. These factors determine what grows here, when frost threatens, and how daily weather unfolds.