Weather in Round Lake Beach, Illinois
Roses open along the stoops. Day 59 of spring. Read this microseason across nine climate regions →
- TodayMay 16Drizzle50%83°60°
- SundayMay 17Heavy Rain33%85°59°
- MondayMay 18Heavy Rain55%78°66°
- TuesdayMay 19Showers56%74°53°
- WednesdayMay 20Overcast13%58°41°
- ThursdayMay 21Overcast—59°40°
- FridayMay 22Overcast—62°46°
- PM 2.5
- 14.3 μg/m³
- PM 10
- 14.9 μg/m³
- NO₂
- 24.7 μg/m³
- Ozone
- 93.0 μg/m³
- UV Index
- 0.0 Low
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 10:32 AM
- Moonset
- 1:40 AM
- In sign
- ♊︎ Gemini
Roses open along the stoops
Round Lake Beach at a glance
- Today vs. normal: 3°F above the seasonal normal for this latitude
- Last frost: April 30 (climatological average for this latitude)
- Microseason: 28 of 72, May 16–20
- Planting window: Direct sow okra, melons, and southern peas. Thin carrot rows.
Right now in the garden
Cool-season window is open
As of May 17, the cool-season window is open or about to open. Direct-sow peas, lettuce, spinach, radishes, and brassicas now. Hold off on warm-season crops until 1–2 weeks after the last spring frost (around May).
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.