· So, what is the difference and how are plants affected by hard frost versus light ones? Keep reading to find out more about the effects of hard frost, including information on hard frost protection. · A hard freeze occurs when the air temperature falls below 28 degrees and stays there for four or more hours. This usually signals the end of the growing season for most plants in Minnesota. · What Is A Hard Freeze? A hard freeze occurs when temperatures drop to 28°F or lower for an extended period during the growing season, explains Kimberly McMahon, public weather services program manager for NWS. This type of freeze can cause damage to both plants and home infrastructure. · The hard freeze happens when temperatures fall below 28 and stay in the low twenties for over 2 or 4 hours. The hard freeze, unlike the frost, it’s extremely damaging and can kill off a significant part of the vegetation in your garden. · First frost vs. hard freeze: learn what they mean for your garden and how to protect plants from cold damage! Learn what constitutes a hard frost and its impact on different plants. Discover how to identify signs of damage and strategies to safeguard your garden. A hard frost occurs when temperatures drop well below freezing, typically below 28 degrees Fahrenheit (-2 degrees Celsius), and persist for a longer period, usually several hours or overnight. · A hard freeze occurs when the air temperature falls below 28 degrees and stays there for four or more hours. This usually signals the end of the growing season for most plants in Minnesota. · What Is A Hard Freeze? A hard freeze occurs when temperatures drop to 28°F or lower for an extended period during the growing season, explains Kimberly McMahon, public weather services program manager for NWS. This type of freeze can cause damage to both plants and home infrastructure. · The hard freeze happens when temperatures fall below 28 and stay in the low twenties for over 2 or 4 hours. The hard freeze, unlike the frost, it’s extremely damaging and can kill off a significant part of the vegetation in your garden. · First frost vs. hard freeze: learn what they mean for your garden and how to protect plants from cold damage! Learn what constitutes a hard frost and its impact on different plants. Discover how to identify signs of damage and strategies to safeguard your garden. A hard frost occurs when temperatures drop well below freezing, typically below 28 degrees Fahrenheit (-2 degrees Celsius), and persist for a longer period, usually several hours or overnight.