USDA Hardiness Zone 6a
Frost Dates for 46077 — Zionsville, Indiana
NOAA 1991–2020 normals from Whitestown, IN (941 ft), 5 miles northwest.
Updated
In Zionsville, the last spring frost (32°F) is around April 21 in half of years and has passed by May 6 in nine years out of ten. The first fall frost comes around October 20, as early as October 5 one year in ten, leaving a typical freeze-free season of 180 days (NOAA, Whitestown, IN).
- Last spring frost
- April 21
- First fall frost
- October 20
- Growing season
- 180 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- December 5
- Last snow
- March 6
- Winters with snow
- 100%
- Snow per year
- 22"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Zionsville
Half of springs at Whitestown, IN see their last 32°F night by April 21; only one in ten is past it by April 6, and one in ten still has one after May 6. Planting tender crops after April 27 leaves a 30% risk of a frost on them, after May 1 20%, and after May 6 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 70% of the 125 Indiana stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 20 in half of years, as early as October 5 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 11 days later, around October 31; in spring the one-in-ten date for 28°F is April 25, 11 days before the 32°F one. The freeze-free season lasts 180 days in a typical year, shorter than at 54% of the 125 Indiana stations; it reaches 200 days one year in ten and falls short of 159 one year in ten. On average 114 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 10 days longer, to about May 1, and return around October 8. Severe cold of 16°F or below comes every winter, usually between December 1 and March 8.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 18 | Apr 22 | Apr 25 | Apr 29 | May 1 | May 3 | May 6 | May 11 | May 17 |
| 32°F | Apr 6 | Apr 12 | Apr 16 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | May 1 | May 6 |
| 28°F | Mar 25 | Mar 31 | Apr 3 | Apr 5 | Apr 9 | Apr 12 | Apr 16 | Apr 20 | Apr 25 |
| 24°F | Mar 11 | Mar 18 | Mar 23 | Mar 27 | Mar 30 | Apr 1 | Apr 3 | Apr 6 | Apr 13 |
| 20°F | Mar 1 | Mar 7 | Mar 11 | Mar 14 | Mar 18 | Mar 22 | Mar 26 | Mar 29 | Apr 2 |
| 16°F | Feb 17 | Feb 26 | Mar 2 | Mar 5 | Mar 8 | Mar 11 | Mar 14 | Mar 20 | Mar 26 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 25 | Sep 30 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 16 | Oct 21 |
| 32°F | Oct 5 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Nov 1 |
| 28°F | Oct 16 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 8 | Nov 13 |
| 24°F | Oct 30 | Nov 2 | Nov 4 | Nov 6 | Nov 10 | Nov 13 | Nov 16 | Nov 22 | Nov 29 |
| 20°F | Nov 5 | Nov 9 | Nov 14 | Nov 17 | Nov 21 | Nov 25 | Nov 30 | Dec 4 | Dec 9 |
| 16°F | Nov 12 | Nov 18 | Nov 23 | Nov 28 | Dec 1 | Dec 5 | Dec 8 | Dec 12 | Dec 19 |
Freeze probabilities 1991–2020 at Whitestown, IN, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 46077 →Compare Zionsville with another place →
Weather by month in Zionsville
July is the warmest month at Whitestown, IN, averaging 83°F by day and 64°F at night; January is the coldest at 33°F and 20°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 21% of years.
Warmth for growing adds up to 3,371 growing degree days a year (base 50°F), more than at 50% of the 125 Indiana stations. 37% of them (1,247) have built up by the end of June, and July adds the most, 728. Precipitation totals 41.5 inches a year, most in June (4.7") and least in February (2.5"); May to September bring 47% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 33 | 20 | 2.9 | 100% | 27 | 2 |
| Feb | 39 | 23 | 2.5 | 100% | 23 | 5 |
| Mar | 50 | 32 | 3.2 | 100% | 18 | 45 |
| Apr | 63 | 42 | 4.3 | 96% | 5 | 162 |
| May | 73 | 53 | 4.6 | 21% | <1 | 402 |
| Jun | 81 | 61 | 4.7 | 0% | 0 | 630 |
| Jul | 83 | 64 | 3.8 | 0% | 0 | 728 |
| Aug | 82 | 62 | 2.9 | 0% | 0 | 679 |
| Sep | 77 | 55 | 3.3 | 3% | <1 | 476 |
| Oct | 65 | 44 | 3.0 | 88% | 4 | 197 |
| Nov | 50 | 34 | 3.4 | 100% | 14 | 39 |
| Dec | 38 | 25 | 2.9 | 100% | 24 | 5 |
Monthly normals 1991–2020 at Whitestown, IN (941 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Indianapolis Eagle Creek Airport, IN, 9 miles south of Zionsville, has a last frost 9 days earlier (April 12), a first frost 9 days later (October 29), a season 18 days longer.
When it snows in Zionsville, Indiana
The first measurable snow (0.1 inch or more) in Zionsville usually arrives around December 5, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Whitestown, IN, 4.5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 46 days after the last snow.
Planting calendar for 46077
| When | What to do |
|---|---|
| February 10 – February 24 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 24 – March 10 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 24 – April 7 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 21 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 28 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 6 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 20 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 46077 is 5 miles from Whitestown, IN, which stands at 941 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 46077 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.