USDA Hardiness Zone 7a
Frost Dates for 18034 — Center Valley, Pennsylvania
NOAA 1991–2020 normals from Springtown 1 NNE, PA (860 ft), 8 miles east.
Updated
In Center Valley, 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 22, as early as October 7 one year in ten, leaving a typical freeze-free season of 184 days (NOAA, Springtown 1 NNE, PA).
- Last spring frost
- April 21
- First fall frost
- October 22
- Growing season
- 184 days
- Hardiness zone
- 7a
50% probability
50% probability
freeze-free, 50%
0 to 5°F (-17.8 to -15.0°C) coldest night
- First snow
- November 28
- Last snow
- April 2
- Winters with snow
- 100%
- Snow per year
- 41.1"
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in Center Valley
Half of springs at Springtown 1 NNE, PA see their last 32°F night by April 21; only one in ten is past it by April 8, 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 72% of the 176 Pennsylvania stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 22 in half of years, as early as October 7 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 12 days later, around November 3; in spring the one-in-ten date for 28°F is April 23, 13 days before the 32°F one. The freeze-free season lasts 184 days in a typical year, longer than at 68% of the 176 Pennsylvania stations; it reaches 205 days one year in ten and falls short of 163 one year in ten. On average 122 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 2, and return around October 10. Severe cold of 16°F or below comes every winter, usually between December 7 and March 11.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 19 | Apr 23 | Apr 26 | Apr 30 | May 2 | May 5 | May 8 | May 12 | May 18 |
| 32°F | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | May 1 | May 6 |
| 28°F | Mar 29 | Apr 2 | Apr 4 | Apr 6 | Apr 8 | Apr 11 | Apr 14 | Apr 18 | Apr 23 |
| 24°F | Mar 16 | Mar 21 | Mar 25 | Mar 29 | Mar 31 | Apr 2 | Apr 4 | Apr 6 | Apr 11 |
| 20°F | Mar 2 | Mar 9 | Mar 14 | Mar 17 | Mar 20 | Mar 24 | Mar 27 | Mar 30 | Apr 2 |
| 16°F | Feb 22 | Feb 28 | Mar 4 | Mar 7 | Mar 11 | Mar 14 | Mar 17 | Mar 20 | Mar 26 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 30 | Oct 2 | Oct 5 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 21 | Oct 26 |
| 32°F | Oct 7 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 26 | Oct 30 | Nov 1 | Nov 6 |
| 28°F | Oct 18 | Oct 24 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 13 | Nov 17 |
| 24°F | Nov 1 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 22 | Nov 26 | Dec 2 |
| 20°F | Nov 10 | Nov 16 | Nov 20 | Nov 23 | Nov 27 | Nov 30 | Dec 3 | Dec 8 | Dec 14 |
| 16°F | Nov 20 | Nov 27 | Dec 1 | Dec 4 | Dec 7 | Dec 11 | Dec 16 | Dec 21 | Dec 29 |
Freeze probabilities 1991–2020 at Springtown 1 NNE, PA, 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 18034 →Compare Center Valley with another place →
Weather by month in Center Valley
July is the warmest month at Springtown 1 NNE, PA, averaging 83°F by day and 62°F at night; January is the coldest at 37°F and 19°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 2,932 growing degree days a year (base 50°F), fewer than at 52% of the 176 Pennsylvania stations. 33% of them (960) have built up by the end of June, and July adds the most, 707. Precipitation totals 53.3 inches a year, most in July (5.6") and least in February (3.2"); May to September bring 46% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 37 | 19 | 3.8 | 100% | 27 | 2 |
| Feb | 40 | 20 | 3.2 | 100% | 25 | 1 |
| Mar | 48 | 28 | 4.4 | 100% | 22 | 19 |
| Apr | 61 | 38 | 4.2 | 99% | 7 | 102 |
| May | 70 | 49 | 4.5 | 22% | <1 | 298 |
| Jun | 78 | 58 | 4.6 | 0% | 0 | 539 |
| Jul | 83 | 62 | 5.6 | 0% | 0 | 707 |
| Aug | 81 | 61 | 4.8 | 0% | 0 | 651 |
| Sep | 75 | 54 | 5.1 | 1% | 0 | 427 |
| Oct | 64 | 43 | 4.9 | 75% | 3 | 152 |
| Nov | 53 | 33 | 3.6 | 100% | 14 | 30 |
| Dec | 42 | 25 | 4.6 | 100% | 25 | 5 |
Monthly normals 1991–2020 at Springtown 1 NNE, PA (860 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, Allentown International Airport, PA, 8 miles north of Center Valley and 470 feet lower, has a last frost 1 day earlier (April 20), a first frost 2 days later (October 24).
When it snows in Center Valley, Pennsylvania
The first measurable snow (0.1 inch or more) in Center Valley usually arrives around November 28, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Springtown 1 NNE, PA, 7.5 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 19 days after the last snow.
Planting calendar for 18034
| 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 30 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 8 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 22 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 18034 is 8 miles from Springtown 1 NNE, PA, which stands at 860 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 18036 (Coopersburg). The 2023 USDA Plant Hardiness Zone Map lists ZIP 18034 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Pennsylvania →
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.