USDA Hardiness Zone 6a
Frost Dates for 46383 — Valparaiso, Indiana
NOAA 1991–2020 normals from Valparaiso Porter Co Municipal Airport, IN (770 ft), 2 miles southeast.
Updated
In Valparaiso, the last spring frost (32°F) is around April 20 in half of years and has passed by May 7 in nine years out of ten. The first fall frost comes around October 26, as early as October 12 one year in ten, leaving a typical freeze-free season of 187 days (NOAA, Valparaiso Porter Co Municipal Airport, IN).
- Last spring frost
- April 20
- First fall frost
- October 26
- Growing season
- 187 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
- November 30
- Last snow
- March 13
- Winters with snow
- 100%
- Snow per year
- 40"
median, 1991–2020
median, 1991–2020
15 of 15 observed
NOAA normal
Frost risk by date in Valparaiso
Half of springs at Valparaiso Porter Co Municipal Airport, IN see their last 32°F night by April 20; only one in ten is past it by April 6, and one in ten still has one after May 7. Planting tender crops after April 27 leaves a 30% risk of a frost on them, after May 1 20%, and after May 7 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 66% of the 125 Indiana stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 26 in half of years, as early as October 12 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 12 days later, around November 7; in spring the one-in-ten date for 28°F is April 23, 14 days before the 32°F one. The freeze-free season lasts 187 days in a typical year, longer than at 66% of the 125 Indiana stations; it reaches 207 days one year in ten and falls short of 166 one year in ten. On average 125 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 11 days longer, to about May 1, and return around October 14. Severe cold of 16°F or below comes every winter, usually between December 6 and March 6.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 18 | Apr 22 | Apr 26 | Apr 29 | May 1 | May 4 | May 8 | May 12 | May 18 |
| 32°F | Apr 6 | Apr 11 | Apr 14 | Apr 17 | Apr 20 | Apr 23 | Apr 27 | May 1 | May 7 |
| 28°F | Mar 23 | Mar 31 | Apr 2 | Apr 5 | Apr 7 | Apr 10 | Apr 13 | Apr 17 | Apr 23 |
| 24°F | Mar 11 | Mar 17 | Mar 21 | Mar 25 | Mar 29 | Mar 31 | Apr 3 | Apr 5 | Apr 10 |
| 20°F | Mar 1 | Mar 6 | Mar 10 | Mar 14 | Mar 17 | Mar 20 | Mar 24 | Mar 28 | Apr 1 |
| 16°F | Feb 16 | Feb 25 | Mar 1 | Mar 4 | Mar 6 | Mar 10 | Mar 13 | Mar 17 | Mar 23 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 30 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 16 | Oct 19 | Oct 22 | Oct 28 |
| 32°F | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 8 |
| 28°F | Oct 25 | Oct 30 | Nov 1 | Nov 3 | Nov 7 | Nov 10 | Nov 13 | Nov 17 | Nov 23 |
| 24°F | Nov 3 | Nov 8 | Nov 12 | Nov 16 | Nov 20 | Nov 23 | Nov 27 | Dec 1 | Dec 6 |
| 20°F | Nov 12 | Nov 18 | Nov 23 | Nov 26 | Nov 30 | Dec 1 | Dec 5 | Dec 10 | Dec 17 |
| 16°F | Nov 21 | Nov 27 | Dec 1 | Dec 3 | Dec 6 | Dec 10 | Dec 14 | Dec 18 | Dec 23 |
Freeze probabilities 1991–2020 at Valparaiso Porter Co Municipal Airport, 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 46383 →Compare Valparaiso with another place →
Frost risk through the year in Valparaiso
In Valparaiso, the spring curve drops under 10% on May 7 and the fall curve passes 10% on October 12, 158 days later; that gap is longer than at 63% of the 125 Indiana stations with frost dates. The spring risk falls from 90% to 10% over 31 days (April 6 to May 7) and the fall risk climbs from 10% to 90% over 27 days (October 12 to November 8): both ends of the season vary about as much. At Valparaiso Wtr Wks, IN, 3 miles north, the same gap runs from May 6 to October 12, 1 day longer.
| Planted on | Another 32°F night | 28°F night |
|---|---|---|
| Apr 6 | over 90% | 55% |
| Apr 13 | 73% | 30% |
| Apr 2050% date | 50% | 15% |
| Apr 27 | 30% | under 10% |
| May 4 | 15% | under 10% |
| May 11 | under 10% | under 10% |
Weather by month in Valparaiso
July is the warmest month at Valparaiso Porter Co Municipal Airport, IN, averaging 85°F by day and 64°F at night; January is the coldest at 34°F and 18°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 22% of years.
Warmth for growing adds up to 3,377 growing degree days a year (base 50°F), more than at 50% of the 125 Indiana stations. 35% of them (1,184) have built up by the end of June, and July adds the most, 763. Precipitation totals 33.3 inches a year, most in June (3.9") and least in February (1.5"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 34 | 18 | 1.6 | 100% | 28 | 1 |
| Feb | 38 | 22 | 1.5 | 100% | 25 | 4 |
| Mar | 49 | 31 | 1.9 | 100% | 21 | 36 |
| Apr | 62 | 40 | 3.3 | 96% | 7 | 130 |
| May | 73 | 51 | 3.7 | 22% | <1 | 374 |
| Jun | 82 | 61 | 3.9 | 0% | 0 | 640 |
| Jul | 85 | 64 | 3.6 | 0% | 0 | 763 |
| Aug | 83 | 62 | 3.9 | 0% | 0 | 707 |
| Sep | 78 | 55 | 2.5 | 1% | 0 | 488 |
| Oct | 65 | 44 | 3.3 | 68% | 3 | 195 |
| Nov | 51 | 34 | 2.4 | 100% | 15 | 36 |
| Dec | 39 | 25 | 1.7 | 100% | 25 | 5 |
Monthly normals 1991–2020 at Valparaiso Porter Co Municipal Airport, IN (770 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, Valparaiso Wtr Wks, IN, 3 miles north of Valparaiso, has a last frost 2 days later (April 22), a first frost 1 day earlier (October 25), a season 2 days shorter.
When it snows in Valparaiso, Indiana
The first measurable snow (0.1 inch or more) in Valparaiso usually arrives around November 30, and the last of the season around March 13. Those are the middle dates across the winters of 1991–2020 at Valparaiso Wtr Wks, IN, 2.6 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 38 days after the last snow.
Planting calendar for 46383
| When | What to do |
|---|---|
| February 9 – February 23 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 23 – March 9 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 23 – April 6 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 20 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 3 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 12 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 26 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 46383 is 2 miles from Valparaiso Porter Co Municipal Airport, IN, which stands at 770 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 46383 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.