Frost Dates for 23701 — Portsmouth, Virginia

Half of springs at Norfolk S, VA see their last 32°F night by March 23; only one in ten is past it by March 7, and one in ten still has one after April 6. Planting tender crops after March 30 leaves a 30% risk of a frost on them, after April 2 20%, and after April 6 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 128 Virginia stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 16 in half of years, as early as November 4 one year in ten, and holds off past December 1 one year in ten. A hard freeze of 28°F follows 15 days later, around December 1; in spring the one-in-ten date for 28°F is March 26, 11 days before the 32°F one. The freeze-free season lasts 239 days in a typical year, longer than at 97% of the 128 Virginia stations; it reaches 262 days one year in ten and falls short of 220 one year in ten. On average 51 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 13 days longer, to about April 5, and return around November 6. Nights of 24°F, cold enough to damage hardier plants, come in 99% of winters and 16°F in 61%.

July is the warmest month at Norfolk S, VA, averaging 88°F by day and 71°F at night; January is the coldest at 49°F and 32°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 25% of years.

Warmth for growing adds up to 4,735 growing degree days a year (base 50°F), more than at 96% of the 128 Virginia stations. 37% of them (1,752) have built up by the end of June, and July adds the most, 916. Precipitation totals 53.6 inches a year, most in August (6.6") and least in February (3.2"); May to September bring 51% of it.

The nearest other station, Norfolk NAS, VA, 11 miles northeast of Portsmouth, has a last frost 7 days earlier (March 16), a first frost 10 days later (November 26), a season 16 days longer.

The first measurable snow (0.1 inch or more) in Portsmouth usually arrives around January 14, and the last of the season around February 21. Those are the middle dates across the winters of 1991–2020 at Norfolk International Airport, VA, 11.7 miles away: half of years saw snow earlier, half later. Snow fell in 83% of those winters. The last 32°F night of spring typically comes 30 days after the last snow.

ZIP 23701 is 9 miles from Norfolk S, VA, which stands at 10 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 19 other ZIP codes share the station; its figures are presented in full for 23464 (Virginia Beach). The 2023 USDA Plant Hardiness Zone Map lists ZIP 23701 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°C) over 1991–2020; a zone describes winter lows, not frost dates.