Weather in Round Lake Heights, Illinois
Roses open along the stoops. Day 59 of spring. Read this microseason across nine climate regions →
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 10:32 AM
- Moonset
- 1:40 AM
- In sign
- ♉︎ Taurus
Roses open along the stoops
Round Lake Heights at a glance
- Today vs. normal: NaN°F below 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
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.