Notes · climate · not a load table

High tunnel USDA zone 4 vs zone 8

Growers comparing a cold-winter house to a warm-winter house keep landing on the same USDA plant-hardiness numbers — then film, row cover, shade, and snow language after the frame lands. This page copies the official 2023 Plant Hardiness Zone Map bands and land-grant season-extension sentences. It does not invent a pound-per-square-foot rating, an EQIP payment, or a planting calendar a source did not print.

Sources retrieved 29 September 2026, about 03:06 UTC (28 September 2026, America/Los_Angeles). USDA ARS Plant Hardiness Zone Map, ARS 15 November 2023 news, Map Creation, PRISM 2023 GIS page, and phzm_us_zones_shp_2023.xml (HTTP 200 zip) were opened live tonight. UAEX MP586, Purdue HO-330-W / HO-297-W / HO-327-W, Rutgers FS1267, Cornell High Tunnels greens, UKY CCD-SP-2, and Bootstrap Farmer Essential Gothic Shopify JSON were re-opened the same night (HTTP 200). Amazon featured one-time prices were copied from live PDPs the same night. Gaps stay an em dash.

Winter row-cover sentences live on winter lettuce in a high tunnel. Shade percent stays on high-tunnel shade cloth. Film grade stays on 6-mil plastic replacement. Vendor gothic snow copy — labeled as vendor copy — is on gothic vs Quonset and Nor'Easter vs Bootstrap 30′ snow. Roll-up sides stay on high-tunnel roll-up sides. Exclusion netting and UGA’s warmer-climate heat caveat stay on high-tunnel insect netting. Width × length is on the size hub.

What zone 4 and zone 8 actually mean

The USDA Agricultural Research Service 2023 Plant Hardiness Zone Map is a winter-temperature map. It is not a snow-load stamp, a wind rating, or a high-tunnel planting calendar.

The map is based on the average annual extreme minimum winter temperature, displayed as 10-degree F zones and 5-degree F half zones.

Source: USDA Agricultural Research Service — 2023 Plant Hardiness Zone Map. Retrieved 29 September 2026, about 03:06 UTC.

Plant hardiness zone designations represent what’s known as the “average annual extreme minimum temperature” at a given location during a particular time period (30 years, in this instance). Put [an]other way, the designations do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature for the location over a specified time.

Source: USDA ARS — USDA Unveils Updated Plant Hardiness Zone Map (15 November 2023). The same news page: The 2023 map is based on 30-year averages of the lowest annual winter temperatures at specific locations, is divided into 10-degree Fahrenheit zones and further divided into 5-degree Fahrenheit half-zones. The 2023 map includes data measured at weather stations from 1991 to 2020. As with the 2012 map, the new version has 13 zones across the United States and its territories. Each zone is broken into half zones, designated as “A” and “B.”

Based on the mean annual extreme minimum temperature over a 30-year period, the map divides the country into zones representing a spread of 10°F (zones 1-13), each subdivided into two half-zones with 5°F spreads (e.g., zone 1a and 1b).

Source: PRISM Climate Group, Oregon State University — 2023 USDA Plant Hardiness Zone GIS Datasets. Official half-zone bands tonight come from PRISM — phzm_us_zones_shp_2023.xml (inside 2023 CONUS shapefile zip), attribute trange: USDA plant hardiness zone mean annual extreme minimum temperature range (degrees Fahrenheit). Copied: 4a: -30 to -25 4b: -25 to -20 8a: 10 to 15 8b: 15 to 20. Map Creation notes the 1991–2020 normals (USDA ARS — Plant Hardiness Zone Map: Map Creation).

Zone 4a is −30 to −25°F; 4b is −25 to −20°F. Zone 8a is 10 to 15°F; 8b is 15 to 20°F. Those are mean annual extreme-minimum bands on the official 2023 shapefile metadata — the average coldest night, not the coldest night on record.

Sourced comparison

Cells below are copied or labeled from the pages opened tonight. A blank cell means that source did not state the figure for that climate. Shade percent is not a degrees-Fahrenheit drop. Gothic snow language is vendor copy, not a PSF.

Cold-climate winter language

Purdue writes Northern-climate and Midwest unheated-tunnel sentences. Those pages do not print a zone-4 high-tunnel planting calendar — that gap stays blank.

High tunnels are plastic-covered structures, big enough to walk in, that provide protection from wind, snow, ice and, with strategic use of row covers, from the coldest temperatures. A common approach to growing cold-tolerant crops in unheated high tunnels during the fall-spring in Northern climates is to plant beds in the late summer/early fall so that plants are mature by end of November, at the latest, at which point plant growth slows considerably until early February. Crops can then be harvested from November-February, using the tunnel as a “living refrigerator” and picking as needed.

Source: Purdue Extension HO-330-W — High Tunnels: Scheduling Fall and Winter Vegetable Production. Cover line: All harvest ranges assume that the grower would use at least medium-weight row cover over beds within the tunnel when nighttime temperatures drop below 25°F and double layer cover if nighttime temperatures drop below 10°F. Vent: high tunnels are vented so as to not allow temperatures above 80°F. Dates: Planting Dates are recommended for Zone 6a, and should be adjusted roughly one week back for Zone 5b and one week forward for Zone 6b.

This publication primarily covers unheated high tunnels and the use of internal row covers. In the Midwest, cool-season crops are grown in these structures from about September through March. It is important to be prepared to vent the tunnel to keep temperatures below 80°F.

Source: Purdue Extension HO-297-W — Managing the Environment in High Tunnels for Cool Season Vegetable Production.

Medium-weight row cover supported on hoops gives 5-10 F warmth, more on colder nights. Gable vents are important for venting during warm spells in the winter, (in addition to roll-up sides used during warmer weather). A higher, taller structure holds heat collected during the day from solar gain better than a shorter, narrower one.

Source: Cornell High Tunnels — Greens. Rutgers: Floating row covers can be used to protect the plants from temperature fluctuations. Row covers used inside a high tunnel add additional insulation to the crop. (Melendez — Ultra-Niche Crops Series: High Tunnel Winter Lettuce (Rutgers NJAES FS1267)). UKY: Row covers used in conjunction with the high tunnel will provide additional cold and frost protection. Because row covers also block sunlight, they should not be left on for prolonged periods during the winter. High tunnels can also make it possible to produce leafy greens and herbs during the winter. (University of Kentucky Center for Crop Diversification CCD-SP-2 — High Tunnel Overview).

Warm-climate winter and summer language

UAEX writes Arkansas and Southeast sentences that still name winter secondary cover — and name shade cloth as necessary for summer production in Arkansas. Purdue HO-327's 30–50% shade line is written for Indiana growers. No page opened tonight writes a zone-8 high-tunnel planting calendar.

Season Extension: Within a high tunnel air and soil temperatures warm more quickly in the spring and stay warmer longer in the fall. Favorable growing environments can also be maintained within a high tunnel through the winter months to support out-of-season production of many cold hardy crops. A secondary cover, often called a row cover or frost blanket, is made from lightweight material and placed over a row (or multiple rows) of plants. Mimicking the high tunnel’s ability to capture heat, the air beneath a secondary cover can be a few degrees (~2-5°F) warmer than the ambient air inside the high tunnel.

Source: University of Arkansas System Division of Agriculture — High Tunnel Production Guide for Arkansas and the Southeast (MP586). Shade: Other costs include plastic replacement, which will need to be done every three to five years, shade cloth (necessary for summer production in Arkansas), irrigation systems and labor to install these coverings.

Indiana growers should use a shade cloth that can reduces light intensity by 30 to 50 percent to ensure optimal light levels for plants, while reducing radiation load for cooling.

Source: Purdue Extension HO-327-W — Temperature Control in Greenhouses (February 2021). That is a light-reduction band, not a promised temperature drop.

How the zone changes kit choices

The zone number does not pick a SKU. It does change which cover sentences land-grants and vendors actually print. None of the following is a load rating.

Film / plastic

When polyethylene is used, Pennsylvania NRCS and CPS 325 both name the same cover: When using a polyethylene cover, a minimum 6-mil greenhouse grade, UV-resistant material is required. UAEX says replacement every three to five years. A 16×90 Amazon sheet is still a short roll — measure the hoop arc. Details stay on 6-mil plastic replacement.

Secondary cover / row cover / frost blanket

Purdue assumes at least medium-weight row cover below 25°F and a double layer below 10°F. Cornell prints 5–10 F warmth from medium-weight cover on hoops. UAEX still names a secondary cover in Arkansas winter and prints about 2–5°F under it. Those sentences live with the crop notes on winter lettuce in a high tunnel.

Shade cloth

UAEX calls shade cloth necessary for summer production in Arkansas. Purdue HO-327 cites 30–50% shade when other cooling is not enough (Indiana growers). No zone-4 shade sentence sat on the pages opened tonight — that cell stays an em dash. Percent comparison stays on high-tunnel shade cloth.

Roll-up sides / ventilation

Purdue vents so the house does not go above 80°F. Cornell names gable vents during winter warm spells and roll-up sides in warmer weather. Which kits include those sides stays on high-tunnel roll-up sides — not re-invented here.

Gothic vs Quonset snow language

Our essential gothic high tunnel kit features the snow shedding gothic arch design that is ideal for Northern climates and areas with winter weather. The steeper roof pitch helps snow slide off instead of accumulating, while the higher endwalls create more headroom and usable interior space.

Source: Bootstrap Farmer Essential Gothic (Shopify JSON re-opened tonight). That is vendor copy, not a stamped load. No pound-per-square-foot figure. Profile notes without a SKU race live on gothic vs Quonset.

Covers should be removed or rolled at the end of the season unless the structure is designed for snow load.

Source: USDA NRCS Pennsylvania — Seasonal High Tunnel System for Crops. Ask the manufacturer and the county whether the structure is designed for snow load. This site does not invent a PSF.

Sizes

Cornell says a higher, taller structure holds daytime solar gain better than a shorter, narrower one. That is not a required width × length. Common commercial rectangles stay on the high-tunnel size hub.

EQIP: structure, not a climate payment

Under the High Tunnel System Initiative, financial assistance is provided only for the structure itself. Electricity, venting systems, lighting, etc. can be installed providing the additions meets manufacturer’s designs and specifications. However, the grower is responsible for those costs.

Source: USDA NRCS High Tunnel System Initiative FAQ (Updated November 2024; Oregon-branded). CPS 325 (NRCS Conservation Practice Standard 325 High Tunnel System) is the practice standard, not a zone-4 or zone-8 payment table. Neither the FAQ nor the Pennsylvania page names zone 4 or zone 8, and neither prints a payment dollar on this site.

EQIP does not pay more because a farm sits in zone 4. This site does not invent an EQIP dollar. Rules vary; call your county NRCS office.

FAQ

What does USDA zone 4 vs zone 8 mean for a high tunnel?

On the 2023 USDA Plant Hardiness Zone Map the number is the average annual extreme minimum winter temperature — the average coldest night, 1991–2020 — not the coldest it has ever been. Official 2023 PRISM metadata: zone 4a −30 to −25°F, 4b −25 to −20°F; zone 8a 10 to 15°F, 8b 15 to 20°F. That is a plant-hardiness band. It is not a snow-load PSF, a wind rating, or an EQIP payment.

Do I need a gothic kit if I farm in zone 4?

No land-grant page opened tonight requires gothic in zone 4. Bootstrap Farmer’s Essential Gothic page sells a “snow shedding gothic arch… ideal for Northern climates.” That is vendor copy, not a stamped load. Pennsylvania NRCS says covers should be removed or rolled at the end of the season unless the structure is designed for snow load — ask the manufacturer and the county. This site does not invent a PSF.

Does EQIP pay more for a high tunnel in zone 4 than in zone 8?

The High Tunnel System Initiative FAQ says financial assistance is provided only for the structure itself; the grower pays for additions such as electricity, venting, and lighting. The Pennsylvania page puts a four-year lifespan on the producer. Neither page names zone 4 or zone 8, and neither prints a payment dollar on this site. Rules vary; call your county NRCS office.

Do I still need row cover inside a zone 8 high tunnel?

UAEX MP586 still names a secondary cover (row cover or frost blanket) for winter and shoulder seasons and prints about 2–5°F warmer air under it. Purdue HO-330’s double-layer line is written for nights below 10°F — colder than zone 8’s official average extreme minimum — and its planting dates are for Zone 6a. Rutgers says floating covers add insulation and cut light. Those are land-grant sentences, not a SKU mandate.

What film do zone 4 and zone 8 kits use?

When polyethylene is used, the Pennsylvania NRCS seasonal high tunnel page and CPS 325 both name a minimum 6-mil greenhouse-grade UV cover. UAEX says plastic replacement every three to five years and names shade cloth as necessary for summer production in Arkansas. Amazon 16×90 and 15×40 sheets on this page are pack sizes, not a 30×96 roof roll.

Tunnel Spec does not sell kits or write EQIP contracts. Published by Pool Party Capital, Inc. Not USDA. Rules vary; call your county NRCS office.