Minnesota Frost Alert: Arctic Blast Hits Tonight—Protect Your Plants, Pipes, and Morning Commute

A sharp drop in overnight temperatures across Minnesota is rekindling worries about frost damage just weeks after many areas logged one of the earliest “last freezes” on record. Meteorologists say a persistent Canadian high-pressure dome is dragging cold, dry air over the Upper Midwest, pushing lows into the 30s and triggering fresh frost advisories for the Twin Cities suburbs, central lakes country and the Arrowhead. Earliest last freeze? Not so fast At Minneapolis–St. Paul International Airport, the mercury has stayed above 32 °F since April 18, positioning 2025 to become the third-earliest last freeze in 153 years of records—if temps can remain above freezing through early June. But climatologists caution that outstate Minnesota historically sees its final frost well into May, and elevations along the North Shore can shiver below 32 °F even in early June. Regions still at risk this week • Twin Cities & southern MN: Patchy frost possible in exurban counties when skies clear and winds drop. • Central MN (St. Cloud, Brainerd, Mille Lacs): Forecast lows 30-34 °F could nip tender annuals. • Northern MN & Iron Range: Hard freeze (≤28 °F) remains plausible, especially in low-lying bogs and river valleys. Gardeners in zone 3 and cooler pockets of zone 4 should plan for at least two more weeks of frost potential. Why the cold snap matters for gardeners Warm weather in early May pushed soil temps above 55 °F, tempting thousands to transplant tomatoes, peppers and basil. Horticulture experts warn those heat-loving crops can suffer tissue damage at 34-36 °F, long before ice crystals form. “Basil, sweet-potato vine and most tropicals really need 55 °F nights—move them inside or row-cover them,” advises Sue Thurber of Sunnyside Gardens in Minneapolis. Protection checklist for a surprise frost • Water late in the afternoon—moist soil releases heat at night. • Drape lightweight frost cloth, old sheets or floating row covers before sunset; secure the edges. • Flip nursery pots or 5-gallon buckets over single vegetable starts. • Disconnect and drain garden hoses to prevent cracking. • For blooming fruit trees, run a low-spray sprinkler overnight if temps dip below 30 °F; the ice film insulates blossoms. Climate signal or spring roulette? State climatologists note that Minnesota’s average last-freeze date has advanced roughly nine days earlier since the 1970s, yet year-to-year volatility is growing. Rapid swings from 80 °F afternoons to sub-freezing dawns are becoming more common as the jet stream stalls, increasing the odds of early warm spells that lure out vegetation, followed by late cold snaps that deliver frost damage. Planting timetable going forward • Warm-season veggies in south & central MN: wait until soil probes read 60 °F—likely late May. • Northern MN gardens: Memorial Day weekend remains the safest line of defense. • Direct-seeding cool crops (spinach, radish, peas): safe statewide; many actually sweeten after light frost. • Perennials & hardy annuals (pansies, snapdragons): can be planted now but cover as needed. When will the risk finally end? Long-range ensembles suggest a sustained warm surge statewide by the first week of June, with overnight lows consistently above 45 °F. Gardeners should still monitor local NWS forecasts nightly; a single radiational-cooling event under clear skies can drop sheltered hollows well below urban readings. Bottom line Minnesota frost season isn’t over yet despite record-early warmth. Keep fabrics, buckets and weather apps handy, and treat the next two weeks as a critical buffer zone. A little vigilance now can save entire beds of tomatoes, petunias and basil—ensuring that once the genuine last freeze passes, your garden is ready to burst into true summer growth.