USDA Hardiness Zone 6b
Frost Dates for 45415 — Dayton, Ohio
NOAA 1991–2020 normals from Dayton International Airport, OH (1,000 ft), 5 miles northeast.
Updated
In Dayton, the last spring frost (32°F) is around April 16 in half of years and has passed by May 3 in nine years out of ten. The first fall frost comes around October 28, as early as October 16 one year in ten, leaving a typical freeze-free season of 194 days (NOAA, Dayton International Airport, OH).
- Last spring frost
- April 16
- First fall frost
- October 28
- Growing season
- 194 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- November 26
- Last snow
- March 26
- Winters with snow
- 100%
- Snow per year
- 25"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Dayton
Half of springs at Dayton International Airport, OH see their last 32°F night by April 16; only one in ten is past it by April 2, and one in ten still has one after May 3. Planting tender crops after April 23 leaves a 30% risk of a frost on them, after April 27 20%, and after May 3 10%. The 17 days between the even-odds date and the one-in-ten date is narrower than at 24% of the 148 Ohio stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 28 in half of years, as early as October 16 one year in ten, and holds off past November 9 one year in ten. A hard freeze of 28°F follows 9 days later, around November 6; in spring the one-in-ten date for 28°F is April 19, 14 days before the 32°F one. The freeze-free season lasts 194 days in a typical year, longer than at 91% of the 148 Ohio stations; it reaches 213 days one year in ten and falls short of 175 one year in ten. On average 110 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 April 27, and return around October 18. Severe cold of 16°F or below comes every winter, usually between December 10 and March 4.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 13 | Apr 17 | Apr 20 | Apr 24 | Apr 27 | Apr 30 | May 3 | May 7 | May 13 |
| 32°F | Apr 2 | Apr 7 | Apr 10 | Apr 14 | Apr 16 | Apr 19 | Apr 23 | Apr 27 | May 3 |
| 28°F | Mar 21 | Mar 27 | Mar 31 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 14 | Apr 19 |
| 24°F | Mar 9 | Mar 15 | Mar 19 | Mar 22 | Mar 25 | Mar 28 | Mar 31 | Apr 3 | Apr 7 |
| 20°F | Feb 25 | Mar 2 | Mar 7 | Mar 12 | Mar 15 | Mar 18 | Mar 22 | Mar 26 | Mar 30 |
| 16°F | Feb 10 | Feb 19 | Feb 26 | Mar 1 | Mar 4 | Mar 8 | Mar 12 | Mar 16 | Mar 21 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 5 | Oct 10 | Oct 13 | Oct 16 | Oct 18 | Oct 21 | Oct 23 | Oct 26 | Oct 30 |
| 32°F | Oct 16 | Oct 20 | Oct 24 | Oct 26 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 9 |
| 28°F | Oct 26 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 16 | Nov 23 |
| 24°F | Nov 1 | Nov 6 | Nov 10 | Nov 13 | Nov 17 | Nov 20 | Nov 25 | Nov 30 | Dec 5 |
| 20°F | Nov 11 | Nov 16 | Nov 21 | Nov 26 | Nov 30 | Dec 3 | Dec 7 | Dec 12 | Dec 20 |
| 16°F | Nov 19 | Nov 27 | Dec 2 | Dec 6 | Dec 10 | Dec 15 | Dec 20 | Dec 25 | Dec 31 |
Freeze probabilities 1991–2020 at Dayton International Airport, OH, 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 45415 →Compare Dayton with another place →
Weather by month in Dayton
July is the warmest month at Dayton International Airport, OH, averaging 86°F by day and 66°F at night; January is the coldest at 37°F and 22°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 15% of years.
Warmth for growing adds up to 3,757 growing degree days a year (base 50°F), more than at 92% of the 148 Ohio stations. 36% of them (1,368) have built up by the end of June, and July adds the most, 806. Precipitation totals 41.6 inches a year, most in April (4.5") and least in February (2.4"); May to September bring 45% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 37 | 22 | 3.1 | 100% | 26 | 6 |
| Feb | 41 | 25 | 2.4 | 100% | 23 | 9 |
| Mar | 52 | 33 | 3.5 | 100% | 17 | 54 |
| Apr | 65 | 43 | 4.5 | 93% | 5 | 182 |
| May | 74 | 54 | 4.5 | 15% | <1 | 438 |
| Jun | 83 | 63 | 4.1 | 0% | 0 | 679 |
| Jul | 86 | 66 | 4.0 | 0% | 0 | 806 |
| Aug | 85 | 64 | 3.0 | 0% | 0 | 758 |
| Sep | 79 | 57 | 3.3 | 0% | 0 | 532 |
| Oct | 66 | 46 | 3.0 | 64% | 2 | 228 |
| Nov | 53 | 35 | 3.1 | 100% | 14 | 54 |
| Dec | 42 | 27 | 3.1 | 100% | 23 | 11 |
Monthly normals 1991–2020 at Dayton International Airport, OH (1,000 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, Dayton Mcd, OH, 6 miles southeast of Dayton and 280 feet lower, has a last frost 2 days later (April 18), a first frost 3 days earlier (October 25), a season 5 days shorter.
When it snows in Dayton, Ohio
The first measurable snow (0.1 inch or more) in Dayton usually arrives around November 26, and the last of the season around March 26. Those are the middle dates across the winters of 1991–2020 at Dayton International Airport, OH, 5.2 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 21 days after the last snow.
Planting calendar for 45415
| When | What to do |
|---|---|
| February 5 – February 19 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 19 – March 5 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 19 – April 2 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 16 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 5 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 14 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 28 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 45415 is 5 miles from Dayton International Airport, OH, which stands at 1,000 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 6 other ZIP codes share the station; its figures are presented in full for 45371 (Tipp City). The 2023 USDA Plant Hardiness Zone Map lists ZIP 45415 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°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.