Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 19966 — Millsboro, DE

ZIP code 19966 (Millsboro, Sussex County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 4 and the first fall frost November 6.

Where ZIP 19966 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not 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.

Zone7b5 to 10 °F
Coldest night−15 to −12.2 °C
Last frostApr 4
First frostNov 6
2012 zone7b

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 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Millsboro, DE…

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 Millsboro, DE

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 4median — 50% chance of a later frost
Safe for tender plantsApril 16only 10% chance of frost after
First fall frostNovember 6median — 10% chance by Oct 23
Growing season217 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 23 and returns around November 19.

From the NOAA station Georgetown Sussex Co. Airport, DE — 9 miles away, elevation 52 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 19966

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 21 – Mar 7
SpinachSow outdoors · Feb 21 – Mar 14
Broccoli, cabbageStart indoors · Jan 24 – Feb 7
Broccoli, cabbageTransplant · Mar 14 – Mar 28
Onion setsPlant outdoors · Mar 7 – Mar 21
PotatoesPlant outdoors · Mar 14 – Mar 28
LettuceSow outdoors · Mar 7 – Mar 21
Carrots, beetsSow outdoors · Mar 14 – Mar 28
TomatoesStart indoors · Feb 7 – Feb 21
TomatoesTransplant · Apr 11 – Apr 25
Peppers, eggplantStart indoors · Jan 24 – Feb 7
Peppers, eggplantTransplant · Apr 18 – May 2
BeansSow outdoors · Apr 11 – Apr 25
Sweet cornSow outdoors · Apr 11 – Apr 25
Cucumbers, squashSow outdoors · Apr 11 – Apr 25
Fall lettuce, spinachSow outdoors · Sep 11 – Sep 25
GarlicPlant cloves · Oct 23 – Nov 27
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 4) and first fall frost (Nov 6) 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 19966 came on Mar 11 — 3 days later than the 1991–2020 average (Mar 8).

JanFebMarAprMayJun

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 Millsboro, DE

The soil mapped at the center of ZIP 19966 is Pepperbox — loamy sand, moderately well drained.

TextureLoamy sanddrains and warms fast; dries out and needs more feeding
pH5.5moderately acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupAwater soaks in fast
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Pepperbox-Rosedale complex, 0 to 2 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 19966; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Millsboro, DE

Summer high88 °Faverage high, July
Winter low29 °Faverage low, January
Hot days31days a year at 90 °F or more
Freezing nights83nights a year at 32 °F or less
Growing degree days4,225base 50 °F — the season’s usable heat
Longest day14 h 52 mindaylight on June 21
Shortest day9 h 28 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation43.9 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 45 °F, low 29 °F 45°29° JanFebruary: average high 48 °F, low 30 °F 48°30° FebMarch: average high 55 °F, low 36 °F 55°36° MarApril: average high 66 °F, low 45 °F 66°45° AprMay: average high 75 °F, low 55 °F 75°55° MayJune: average high 83 °F, low 64 °F 83°64° JunJuly: average high 88 °F, low 70 °F 88°70° JulAugust: average high 86 °F, low 68 °F 86°68° AugSeptember: average high 80 °F, low 61 °F 80°61° SepOctober: average high 69 °F, low 49 °F 69°49° OctNovember: average high 59 °F, low 40 °F 59°40° NovDecember: average high 50 °F, low 33 °F 50°33° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.01 in precipitation 3.0 JanFebruary: 2.58 in precipitation 2.6 FebMarch: 3.86 in precipitation 3.9 MarApril: 3.29 in precipitation 3.3 AprMay: 3.63 in precipitation 3.6 MayJune: 4.07 in precipitation 4.1 JunJuly: 4.14 in precipitation 4.1 JulAugust: 3.99 in precipitation 4.0 AugSeptember: 4.54 in precipitation 4.5 SepOctober: 4.11 in precipitation 4.1 OctNovember: 3.19 in precipitation 3.2 NovDecember: 3.47 in precipitation 3.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Georgetown Sussex Co. Airport, DE (9 mi away); precipitation: Georgetown Sussex Co. Airport, DE (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

199397b
Dagsboro, DE · 4 mi
199457b
Frankford, DE · 6 mi
199517b
Harbeson, DE · 7 mi
199677b
Millville, DE · 9 mi
199477b
Georgetown, DE · 9 mi
199757b
Selbyville, DE · 10 mi
199708a
Ocean View, DE · 10 mi
199308a
Bethany Beach, DE · 11 mi

Delaware planting zones →

Questions about 19966

What planting zone is ZIP code 19966?

ZIP code 19966 (Millsboro, DE) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Millsboro, DE?

The median last spring frost (32 °F) near 19966 is April 4; after April 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Georgetown Sussex Co. Airport station.

When is the first frost in Millsboro, DE?

The median first fall frost near 19966 is November 6, giving a median frost-free growing season of 217 days.

When should I plant tomatoes in 19966?

Start tomato seeds indoors around Feb 7 – Feb 21 and set transplants outside around Apr 11 – Apr 25, one to three weeks after the median last frost.

How much rain and snow does 19966 get?

About 43.9 inches of precipitation a year (NOAA 1991–2020 normals, Georgetown Sussex Co. Airport station).

How hot do summers get in Millsboro, DE?

The average high peaks at 88 °F in July, with about 31 days a year at 90 °F or more.

What kind of soil does 19966 have?

The USDA soil survey maps Pepperbox at the center of ZIP 19966: loamy sand, moderately well drained, pH about 5.5 (moderately acidic).

Did spring come early in Millsboro, DE in 2026?

Spring leaf-out near 19966 came on Mar 11 in 2026, 3 days later than the 1991–2020 average (Mar 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Millsboro, DE?

Intermediate onions: the longest day near 19966 is 14 h 52 min, so day-neutral types bulb best; long-day varieties may not bulb fully.