Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 60033 — Harvard, IL

ZIP code 60033 (Harvard, McHenry County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 28 and the first fall frost October 12.

Where ZIP 60033 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostApr 28
First frostOct 12
2012 zone5b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Harvard, IL…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Harvard, IL

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 28median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 12median — 10% chance by Sep 28
Growing season166 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 18 and returns around October 25.

From the NOAA station Marengo, IL — 11 miles away, elevation 814 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 60033

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 17 – Mar 31
SpinachSow outdoors · Mar 17 – Apr 7
Broccoli, cabbageStart indoors · Feb 17 – Mar 3
Broccoli, cabbageTransplant · Apr 7 – Apr 21
Onion setsPlant outdoors · Mar 31 – Apr 14
PotatoesPlant outdoors · Apr 7 – Apr 21
LettuceSow outdoors · Mar 31 – Apr 14
Carrots, beetsSow outdoors · Apr 7 – Apr 21
TomatoesStart indoors · Mar 3 – Mar 17
TomatoesTransplant · May 5 – May 19
Peppers, eggplantStart indoors · Feb 17 – Mar 3
Peppers, eggplantTransplant · May 12 – May 26
BeansSow outdoors · May 5 – May 19
Sweet cornSow outdoors · May 5 – May 19
Cucumbers, squashSow outdoors · May 5 – May 19
Fall lettuce, spinachSow outdoors · Aug 17 – Aug 31
GarlicPlant cloves · Sep 28 – Nov 2
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 28) and first fall frost (Oct 12) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 60033 came on Mar 30 — 11 days earlier than the 1991–2020 average (Apr 10).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 5b in Illinois

584 plants native to the lower 48 states, recorded in Illinois, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 77

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 102

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °F

Wildflowers & perennials 210

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 173

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °F

Vines 7

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet honeysuckle16 ft · blooms late summer · low shade tolerance · to −33 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Harvard, IL.

Soil in Harvard, IL

The soil mapped at the center of ZIP 60033 is Kidami — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables
pH6.2slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classprime farmlandUSDA classification

Map unit: Kidami silt loam, 4 to 6 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 60033; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harvard, IL

Summer high84 °Faverage high, July
Winter low13 °Faverage low, January
Hot days15days a year at 90 °F or more
Freezing nights147nights a year at 32 °F or less
Growing degree days2,850base 50 °F — the season’s usable heat
Longest day15 h 18 mindaylight on June 21
Shortest day9 h 04 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation37.5 inper year, rain and melted snow
Snowfall32 inper year; 57 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 29 °F, low 13 °F 29°13° JanFebruary: average high 33 °F, low 16 °F 33°16° FebMarch: average high 45 °F, low 26 °F 45°26° MarApril: average high 59 °F, low 36 °F 59°36° AprMay: average high 70 °F, low 47 °F 70°47° MayJune: average high 80 °F, low 57 °F 80°57° JunJuly: average high 84 °F, low 62 °F 84°62° JulAugust: average high 82 °F, low 60 °F 82°60° AugSeptember: average high 75 °F, low 52 °F 75°52° SepOctober: average high 62 °F, low 40 °F 62°40° OctNovember: average high 47 °F, low 29 °F 47°29° NovDecember: average high 35 °F, low 19 °F 35°19° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 1.74 in precipitation, 10 in snowfall 1.7❄10 JanFebruary: 1.70 in precipitation, 8.4 in snowfall 1.7❄8 FebMarch: 2.25 in precipitation, 4.4 in snowfall 2.3❄4 MarApril: 3.57 in precipitation, 0.7 in snowfall 3.6❄1 AprMay: 4.45 in precipitation 4.5 MayJune: 4.94 in precipitation 4.9 JunJuly: 3.74 in precipitation 3.7 JulAugust: 4.06 in precipitation 4.1 AugSeptember: 3.71 in precipitation 3.7 SepOctober: 2.93 in precipitation 2.9 OctNovember: 2.41 in precipitation, 2.1 in snowfall 2.4❄2 NovDecember: 2.03 in precipitation, 6.3 in snowfall 2.0❄6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Marengo, IL (11 mi away); precipitation: Harvard, IL (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

531845b
Walworth, WI · 7 mi
610125b
Capron, IL · 8 mi
531955b
Zenda, WI · 9 mi
531255b
Fontana, WI · 9 mi
535855b
Sharon, WI · 9 mi
600345b
Hebron, IL · 10 mi
600985b
Woodstock, IL · 10 mi
600395b
Crystal Lake, IL · 11 mi

Illinois planting zones →

Questions about 60033

What planting zone is ZIP code 60033?

ZIP code 60033 (Harvard, IL) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Harvard, IL?

The median last spring frost (32 °F) near 60033 is April 28; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Marengo station.

When is the first frost in Harvard, IL?

The median first fall frost near 60033 is October 12, giving a median frost-free growing season of 166 days.

When should I plant tomatoes in 60033?

Start tomato seeds indoors around Mar 3 – Mar 17 and set transplants outside around May 5 – May 19, one to three weeks after the median last frost.

How much rain and snow does 60033 get?

About 37.5 inches of precipitation a year and 32 inches of snowfall (NOAA 1991–2020 normals, Harvard station).

How hot do summers get in Harvard, IL?

The average high peaks at 84 °F in July, with about 15 days a year at 90 °F or more.

What kind of soil does 60033 have?

The USDA soil survey maps Kidami at the center of ZIP 60033: silt loam, moderately well drained, pH about 6.2 (slightly acidic).

Did spring come early in Harvard, IL in 2026?

Spring leaf-out near 60033 came on Mar 30 in 2026, 11 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harvard, IL?

Long-day onions: the longest day near 60033 is 15 h 18 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).