Surprise Minnesota Frost Tonight: Critical Tips to Protect Your Garden and Pipes

A fresh shot of Canadian air is poised to chill parts of Minnesota overnight, triggering a frost advisory for the Arrowhead and portions of northeastern counties from 1 a.m. to 9 a.m. Friday, May 23. Forecasters expect valley lows to slip into the lower 30s, cold enough for a light freeze on exposed vegetation, especially in low-lying areas and sheltered clearings. Although the Twin Cities logged an unusually early “last spring freeze” this year—April 24 on average, with 2025 potentially ranking among the earliest final freezes on record—northern Minnesota often faces frost threats well into late May. Gardeners in Duluth, Ely, Hibbing and Grand Marais should delay planting tender annuals or be ready to protect tomatoes, peppers and flowering baskets with row covers, old bedsheets or overturned buckets until morning sun arrives. Why the lingering chill? Clear skies, light winds and low dew points behind a departing cold front allow rapid radiational cooling after sunset. When surface temperatures drop to 32 °F (0 °C) or below for even a short window, ice crystals can damage leaf cells, leading to wilted or blackened foliage by sunrise. Newly emerged soybean and sugar-beet seedlings, early sweet-corn stands and blossoming apple or cherry trees are especially vulnerable. Soil temperatures across central Minnesota are already hovering in the mid-50s, meaning the ground will release some stored warmth overnight. Still, planters who tucked transplants into raised beds or containers—where soil cools faster—should water thoroughly before dusk; moist soil retains heat better than dry, sandy ground. Move potted herbs and hanging baskets against a south-facing wall or into an unheated garage for the night. The good news: once Friday morning frost lifts, a sunny stretch settles in for the Memorial Day weekend. Highs in the 60s to near 70 across southern Minnesota and upper 50s to low 60s along the North Shore will encourage rapid rebound. Overnight lows look to moderate into the 40s statewide by Sunday, signaling the gradual close of Minnesota’s frost window for most locations. Long-term climate records show that even northern counties seldom record frost after the first week of June, so gardeners craving warm-season crops may only need to hold out a dozen more days. Until then, keep lightweight covers handy, tune in to local National Weather Service bulletins for “frost advisory” and “freeze warning” updates, and remember: in Minnesota, spring isn’t truly safe until you’ve packed away both your ice scraper and your extra row fabric.