Zones / 4b

Zone 4b

In the 2023 PRISM ZIP table, zone 4b is labeled with an average annual extreme minimum of -25°F to -20°F. 1,256 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 April 24 to May 14. That is a range across stations, not a zone-wide frost normal. USDA does not publish a single frost date per half-zone.

• Rochester, MNZIP 55903 · 2.2 miles from the city point
• Duluth, MNZIP 55806 · 0.5 miles from the city point
• Lakeville, MNZIP 55044 · 2.6 miles from the city point
• Eau Claire, WIZIP 54703 · 1.7 miles from the city point
• St. Cloud, MNZIP 56387 · 3.5 miles from the city point
• Great Falls, MTZIP 59401 · 1.2 miles from the city point

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