Planting zone for 18966 — Southampton, PA
ZIP code 18966 (Southampton, Bucks County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 21 and the first fall frost October 25.
Where ZIP 18966 is
Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoomNot the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.
Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7a means →
Frost forecast — next 7 nights
live from the National Weather ServiceLoading the forecast for Southampton, PA…
Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.
Frost dates in Southampton, PA
A hard freeze (28 °F) usually ends around April 8 and returns around November 3.
From the NOAA station Neshaminy Falls, PA — 4 miles away, elevation 39 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.
When to plant vegetables in 18966
Counted from the median last spring frost (Apr 21) and first fall frost (Oct 25) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.
When spring arrived in 2026
In 2026, spring leaf-out near 18966 came on Mar 22 — about the same time as the 1991–2020 average (Mar 24).
Mar 242026
Mar 22
The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).
Soil in Southampton, PA
The soil mapped at the center of ZIP 18966 is Penn — channery silt loam, well drained. Much of the area is built over (urban land); this is the natural soil underneath.
Map unit: Urban land-Penn complex, 0 to 8 percent slopes.
Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 18966; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Southampton, PA
Average high and low, by month
Precipitation by month inches · ❄ = snowfall
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Neshaminy Falls, PA (4 mi away); precipitation: Neshaminy Falls, PA (4 mi away). Daylight is calculated from latitude.
Nearby ZIP codes
3 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.
Questions about 18966
What planting zone is ZIP code 18966?
ZIP code 18966 (Southampton, PA) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).
When is the last frost in Southampton, PA?
The median last spring frost (32 °F) near 18966 is April 21; after May 7 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Neshaminy Falls station.
When is the first frost in Southampton, PA?
The median first fall frost near 18966 is October 25, giving a median frost-free growing season of 185 days.
When should I plant tomatoes in 18966?
Start tomato seeds indoors around Feb 24 – Mar 10 and set transplants outside around Apr 28 – May 12, one to three weeks after the median last frost.
How much rain and snow does 18966 get?
About 50.7 inches of precipitation a year and 20 inches of snowfall (NOAA 1991–2020 normals, Neshaminy Falls station).
How hot do summers get in Southampton, PA?
The average high peaks at 86 °F in July, with about 27 days a year at 90 °F or more.
What kind of soil does 18966 have?
The USDA soil survey maps Penn at the center of ZIP 18966: channery silt loam, well drained, pH about 5.4 (strongly acidic).
Did spring come early in Southampton, PA in 2026?
Spring leaf-out near 18966 came on Mar 22 in 2026, about the same as the 1991–2020 average (Mar 24), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Southampton, PA?
Long-day onions: the longest day near 18966 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).