Zones / 4a

Zone 4a

In the 2023 PRISM ZIP table, zone 4a is labeled with an average annual extreme minimum of -30°F to -25°F. 783 ZIP codes carry that half-zone. USDA’s map page describes these bands as 5°F half-zones inside 10°F zones.

Among cities on this site in this half-zone, the median last 32°F date at each city’s station runs from May 5 to May 10. That is a range across stations, not a zone-wide frost normal. USDA does not publish a single frost date per half-zone.

• Fargo, NDZIP 58103 · 0.7 miles from the city point
• Bismarck, NDZIP 58505 · 0.7 miles from the city point
• Grand Forks, NDZIP 58201 · 4.4 miles from the city point
• Minot, NDZIP 58703 · 6 miles from the city point
• Moorhead, MNZIP 56563 · 0.5 miles from the city point
• West Fargo, NDZIP 58078 · 1.9 miles from the city point

Source: PRISM 2023 PHZM ZIP CSV and USDA Plant Hardiness Zone Map.