What does USDA hardiness zone 5a mean in Pennsylvania?

Zone 5a means an average annual extreme minimum winter temperature of −20 to −15 °F — the standard USDA measure of which perennials survive winter. 1 location in Pennsylvania fall in this zone. It does not set planting dates; see the frost calendar below for that.

When should I plant tomatoes in Pennsylvania's zone 5a?

Using Smethport's frost dates (this page's median-season location): start seeds indoors about Mar 20 – Apr 3, then transplant outside about May 22 – May 29. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.

Does every location in Pennsylvania's zone 5a have the same frost dates?

No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).

USDA zone 5a in Pennsylvania

−20 to −15 °F avg. annual extreme minimum · 1 location in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 5a covers 1 location across Pennsylvania (average annual extreme minimum −20 to −15 °F): Smethport, PA. Average last spring frost across this group ranges May 15 and growing seasons run 140 days — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Pennsylvania location's own frost dates; the printable planting calendar uses Smethport, this group's median-season location.

USDA zone: 5a−20 to −15 °F
Last frost range: May 15avg, 32°F
First frost range: Oct 3avg, 32°F
Growing season range: 140days

Locations in this group

Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Smethport *	—	Clermont 1 Nw	May 15	Oct 3	140

* Smethport is this group's median-season location — the calendar below is computed from its data.

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.

Planting calendar (Smethport, representative)

Computed from Smethport's average frost dates — the median-season location in this Pennsylvaniazone 5a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Smethport (Pennsylvania, zone 5a), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Mar 20 – Apr 3	May 22 – May 29	Jul 21 – Aug 10	—	matures comfortably
Pepper	Very tender	Mar 6 – Mar 20	May 29 – Jun 5	Jul 28 – Aug 27	—	matures comfortably
Cucumber	Tender	Apr 17 – Apr 24	May 22 – May 29	Jul 11 – Jul 31	—	matures comfortably
Summer squash / zucchini	Tender	—	May 22 – May 29	Jul 6 – Jul 21	—	matures comfortably
Bush bean	Tender	—	May 22 – May 29	Jul 11 – Jul 21	Aug 4 – Aug 14	matures comfortably
Sweet corn	Tender	—	May 15 – May 29	Jul 14 – Aug 13	—	matures comfortably
Basil	Very tender	Apr 3 – Apr 17	May 22 – May 29	Jun 21 – Jul 6	—	matures comfortably
Lettuce	Half-hardy	Apr 3 – Apr 17	Apr 17 – May 1	Jun 1 – Jun 16	Jul 21 – Aug 5	matures comfortably
Pea	Hardy	—	Apr 3 – Apr 17	May 28 – Jun 12	Jul 11 – Jul 26	matures comfortably
Spinach	Hardy	—	Apr 3 – Apr 17	May 13 – May 23	Jul 31 – Aug 10	matures comfortably
Carrot	Half-hardy	—	Apr 24 – May 1	Jun 23 – Jul 13	Jul 1 – Jul 21	matures comfortably
Broccoli	Half-hardy	Mar 20 – Apr 3	Apr 17 – May 1	Jun 11 – Jul 1	Jul 6 – Jul 26	matures comfortably

Which crops fit this growing season

Using Smethport's own 140-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.

Frost & freeze dates (Smethport)

From NOAA's 1991–2020 Climate Normals at station USC00361526. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Smethport.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	May 29	Jun 11	Sep 23	Oct 4	116
32°F (freeze)	May 15	May 31	Oct 3	Oct 18	140
28°F	May 4	May 20	Oct 16	Nov 1	165
24°F	Apr 21	May 7	Oct 31	Nov 15	192

Growing degree days

Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 1 locations is 1,804; Smethport's own reading is shown below.

Annual growing degree days for Smethport (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	1,804	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	3,680	cool-season crops (brassicas, greens)

Hardiness zone 5a in Pennsylvania

Zone 5a means an average annual extreme minimum winter temperature of about −20 to −15 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Pennsylvania spans 7 hardiness zones in this dataset — see all Pennsylvania locations for the full range, including zones5b, 6a, 6b, 7a, 7b, 8a.

Explore zone 5a in other states at zone 5a, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 5a mean in Pennsylvania?: Zone 5a means an average annual extreme minimum winter temperature of −20 to −15 °F — the standard USDA measure of which perennials survive winter. 1 location in Pennsylvania fall in this zone. It does not set planting dates; see the frost calendar below for that.
When should I plant tomatoes in Pennsylvania's zone 5a?: Using Smethport's frost dates (this page's median-season location): start seeds indoors about Mar 20 – Apr 3, then transplant outside about May 22 – May 29. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
Does every location in Pennsylvania's zone 5a have the same frost dates?: No — they do not all share a weather station, so frost dates vary by a week or more across the 1 locations listed (see the table above for each location's own dates).

Sources & method

Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.