When to plant in Merrillville, IN
USDA Zone 6aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Merrillville, Indiana — all computed from Merrillville's nearest NOAA weather station.
Merrillville's nearest full-normals station sits about 24 km out, so treat these as a close estimate — local microclimate can nudge your first and last frost. In zone 6a, Merrillville gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
The average first fall frost in Merrillville is now 5 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
VALPARAISO WTR WKS · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Merrillville’s own odds, recorded at VALPARAISO WTR WKS.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 22 | May 4 | Apr 20 | Sep 30 | Oct 13 | Oct 26 |
| 32°F | May 6 | Apr 22 | Apr 7 | Oct 12 | Oct 25 | Nov 6 |
| 28°F | Apr 24 | Apr 9 | Mar 25 | Oct 24 | Nov 5 | Nov 21 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Merrillville, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 26 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Merrillville planting FAQ
When is the last spring frost in Merrillville, IN?
Merrillville's average last spring frost falls near April 22 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Merrillville, IN?
The first fall frost in Merrillville typically arrives around October 25 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Merrillville in?
Merrillville is in USDA hardiness zone 6a. In zone 6a, winters are moderate — most common vegetables grow well in season.
How long is the growing season in Merrillville?
Merrillville has about 186 frost-free days — a moderate growing season — between the average last spring frost (April 22) and first fall frost (October 25).
When should I plant tomatoes in Merrillville?
For Merrillville, sow tomatoes indoors about February 25–March 11 and move the seedlings out around April 29, after the last spring frost.
Never miss a window in Merrillville
An email when it’s time to start seeds, transplant, and sow — timed to Merrillville’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Hobart · 6 km
- Crown Point · 7 km
- Schererville · 11 km
- Griffith · 11 km
- Lake Station · 13 km
- St. John · 13 km
- Gary · 13 km
- Highland · 14 km
Frost dates recorded at VALPARAISO WTR WKS, 24 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Merrillville, IN — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00128999. Retrieved from https://blissgarden.com/indiana/merrillville.