When is the last frost in Bethlehem, PA?

The average last spring frost (50% probability of 32°F) in Bethlehem is around April 21, based on NOAA/NCEI 1991–2020 normals at the Springtown 1 Nne, PA station (4.8 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Bethlehem?

The average first fall frost in Bethlehem, PA is around October 22, giving roughly a 184-day frost-free growing season.

What planting zone is Bethlehem, PA?

Bethlehem is in USDA plant hardiness zone 7a (average annual extreme minimum temperature 0 to 5°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Bethlehem?

In Bethlehem, PA the warmest month is July (avg high 83.2°F) and the coldest is January (avg low 19.3°F). It averages about 53.4″ of precipitation a year and 41.1″ of snow.

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Bethlehem, PA Planting Calendar & Frost Dates

USDA hardiness zone 7a · ZIP 18015 · elevation 262′ · NOAA & USDA data

Bethlehem is in USDA hardiness zone 7a (winters can dip to 0 to 5°F), with a growing season of about 184 days between the average last spring frost (April 21) and first fall frost (October 22). The warmest month is July (avg high 83.2°F); the coldest is January (avg low 19.3°F). It averages 53.4″ of precipitation a year and 41.1″ of snow, mostly mid-winter. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp 0 to 5°F

Last spring frost

April 21

avg (50% prob, 32°F)

First fall frost

October 22

avg (50% prob, 32°F)

Growing season

184 days

frost-free window

Warmest month

July

avg high 83.2°F

Month-by-month typical weather in Bethlehem

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Springtown 1 Nne, PA (4.8 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	36.9	19.3	28.1	3.8	10.5
February	40	20.4	30.2	3.2	12.1
March	48.3	27.5	37.9	4.4	8.5
April	60.8	38.2	49.5	4.2	1.3
May	70.1	48.5	59.3	4.5	0
June	78.2	57.7	68	4.6	0
July	83.2	62.4	72.8	5.6	0
August	81.3	60.7	71	4.8	0
September	74.7	53.6	64.2	5.1	0
October	63.5	42.6	53	4.9	0.6
November	52.5	33	42.7	3.6	1.7
December	41.7	25.1	33.4	4.6	6.4

What to plant when in Bethlehem

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: March 10 · Transplant out: April 28
Peppers	warm	Start seeds indoors: February 24 · Transplant out: May 5
Cucumbers	warm	Direct sow: April 28
Zucchini / squash	warm	Direct sow: April 28
Bush beans	warm	Direct sow: April 28
Sweet corn	warm	Direct sow: April 28
Basil	warm	Transplant out: April 28
Peas	cool	Sow (spring): March 17 · Sow (fall): August 27
Spinach	cool	Sow (spring): March 10 · Sow (fall): August 27
Lettuce	cool	Sow (spring): March 24 · Sow (fall): August 27
Kale	cool	Transplant (spring): March 31 · Sow (fall): August 13
Broccoli	cool	Transplant (spring): April 7
Carrots	cool	Sow (spring): March 31 · Sow (fall): August 13
Onions	cool	Transplant (spring): March 24
Potatoes	cool	Plant seed potatoes: April 7
Radishes	cool	Sow (spring): March 24 · Sow (fall): September 10

Dates are computed from Bethlehem's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

Nearby cities in Pennsylvania

Reading, PA Philadelphia, PA Scranton, PA Lancaster, PA Harrisburg, PA York, PA State College, PA Altoona, PA

Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Springtown 1 Nne, PA, 4.8 mi (confidence: high). Monthly weather normals: Springtown 1 Nne, PA, 4.8 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.