What Is a Hard Freeze? What the Term Means Where You Live
A forecast calls for a hard freeze at 28°F, but a nearby weather station uses 25°F. Then another forecast mentions 24°F. Which number should you trust? It depends on the weather office and the definition it uses. The National Weather Service (NWS) has a national definition, but local criteria can differ. Knowing what a hard freeze means helps you protect your plants, pipes, pets, and home before temperatures drop. It also gives you time to plan for a possible power outage.
The short answer: 28°F (usually), for an extended period
The NWS defines a hard freeze as surface air temperatures reaching 28°F or lower for an extended period. That last part matters. A brief dip below 28°F isn't necessarily the same as a prolonged stretch of freezing weather. The definition also reflects the damage hard freezes can cause, including killing most types of vegetation.
Freeze vs. hard freeze vs. frost
These terms describe different conditions, even though weather reports sometimes use them interchangeably.
Term | NWS glossary wording | What it means at home |
Frost | Thin ice crystals on the ground or other surfaces; forms when surfaces drop below freezing, often with air temperatures in the mid-30s°F | Tender plants at risk; ice on windshields |
Freeze | Surface air temperature expected to be 32°F or below over a widespread area for a climatologically significant period | Tender plants and exposed outdoor water lines at risk |
Hard freeze | Surface air temperature reaches 28°F or lower for an extended period, killing most types of vegetation | Most seasonal plants damaged; exposed pipes need protection |
People also search for a hard frost definition. The NWS glossary doesn't formally define "hard frost." In everyday use, people often mean a hard freeze when they use that phrase.
Why air temperature matters
Official air temperature readings are generally taken about 6.5 feet above the ground. The ground, plants, and other exposed surfaces can get colder than the reported air temperature, which helps explain why frost can appear even when a thermometer reads above 32°F. When a freeze warning appears in your forecast, start preparing before the cold arrives. These freeze preparation steps can help you get your home ready for severe winter weather. The 28°F threshold is a useful starting point, but it isn't the only number you'll see.
Why Your Local Forecast Might Use a Different Number
Weather offices consider local climate and growing conditions when issuing freeze alerts. A hard freeze in north Florida may use different criteria from one in the Upper Midwest. The NWS Tallahassee office notes that the definition can vary from one office to another.
Source | Hard freeze threshold as stated | Notes |
NWS glossary | 28°F or lower for an extended period | National definition |
NWS Raleigh (Frost/Freeze page) | Hard Freeze Warning when temperatures expected to be 28°F or less | This former warning name was consolidated into Freeze Warning in 2024. |
NWS St. Louis (frost/freeze page) | Falls to or below 28°F; can kill nearly all seasonal plants | Local definition |
NWS Tallahassee (frost and freeze info) | Hard freeze set at 25°F | Office says definitions vary |
Western Regional Climate Center (NOAA partner) | Uses "severe freeze" for 24°F and less; moderate freeze 25°F to 28°F; light freeze 29°F to 32°F | Plant-damage scale, not an alert product |
These numbers serve different purposes. A local weather office's alert criteria aren't necessarily the same as a climate center's scale for plant damage. Check the wording in your local forecast rather than relying on a single number from another state.
What changed with NWS freeze alerts in 2024?
On October 1, 2024, the NWS consolidated Hard Freeze Warnings into Freeze Warnings and renamed Hard Freeze Watches as Freeze Watches. The term "hard freeze" can still appear in a Freeze Warning when the forecast calls for minimum shelter temperatures of 28°F or lower.
That means you may see a Freeze Warning rather than a separate Hard Freeze Warning. Local offices can also apply their own rules about when to issue alerts, so read the details in the forecast. Before the first major freeze, disconnect garden hoses, cover tender plants, and store outdoor tools. If severe winter weather could also cause power outages in your area, it's worth planning how you'll keep essential devices running.
If Your Area Faces Outage Risk Too: Two Power Lists to Plan Ahead
A hard freeze doesn't automatically mean you'll lose power. But ice, strong winds, and heavy electricity demand can contribute to outages in some areas. Before cold weather arrives, separate the devices you need for everyday life from the home equipment that may require a professionally installed backup connection. Stored power can help run selected devices, but it doesn't replace pipe insulation, winterizing, or furnace repairs. It also can't guarantee that your pipes won't freeze.
List 1: daily-life loads (120V)
Start with the appliances you use daily and small devices that help protect pipes from freezing.
Keep your refrigerator, lights, Wi-Fi router, modem, and phone chargers running.
For pipe freeze protection, check that heat tape or heating cables are approved for use with your power station. Check the product label for running and startup wattage before connecting them.
List 2: approved home circuits (may include 240V)
For larger equipment, check its power requirements and whether it needs a dedicated circuit before choosing a backup power station.
Well pumps and heating equipment may need more power or a dedicated circuit. Check the equipment's voltage and wattage, and consult a licensed electrician to confirm compatibility.
EcoFlow TITAN units are rated IP20 for indoor use and cannot charge below 32°F. Keep them in a protected indoor space where temperatures stay above freezing.
For larger loads that need 240V power, the EcoFlow TITAN 5000 offers split-phase output for compatible home equipment.
How the two products divide the job
The EcoFlow TITAN 5000 Classic suits everyday 120V essentials, while the EcoFlow TITAN 5000 also supports compatible 240V equipment. Choose based on the appliances you need to keep running.
EcoFlow TITAN 5000 Classic: Provides 4,000W of rated 120V AC output for appliances such as refrigerators, lights, routers, and compatible pipe-heating devices. It does not support 240V equipment.
EcoFlow TITAN 5000: Provides 7,200W of split-phase 120V/240V output for compatible equipment, such as a well pump or heating circuit. Connecting selected home circuits requires a Smart Home Panel 10 installed by a licensed electrician.
For either model: Check each appliance's running and startup wattage, the usable battery capacity, and the temperature where the unit will operate. A battery backup does not replace pipe insulation or other winterizing measures.
Example: how long list 1 could last (labeled estimate)
You can estimate runtime by multiplying the battery capacity by 0.85 to account for conversion losses, then dividing by the average power draw.
Usable energy: 5,000Wh × 0.85 = 4,250Wh.
Example load: At an average draw of 250W, a refrigerator, lights, and router could run for about 17 hours (4,250Wh ÷ 250W).
The 250W figure is an example, not a guaranteed load. Refrigerators cycle on and off, so actual consumption varies. Use measured power draw where possible to get a more realistic estimate. Before choosing a system for selected home circuits, see how the Smart Home Panel works and discuss your setup with a licensed electrician. With backup power covered, let's look at the four things a hard freeze can affect most.
Plants, Pipes, Pets and People: What a Hard Freeze Puts at Risk
A hard freeze can damage much more than the plants in your yard. The longer temperatures stay low, the more important it becomes to protect exposed plumbing, bring pets indoors, and make sure everyone has a safe way to stay warm.
Plants: A moderate freeze can damage much of the vegetation in your yard. Ice can form inside plant cells and rupture them. Bring potted plants indoors when possible, and cover tender outdoor plants before temperatures fall.
Pipes: Exposed plumbing is vulnerable to freezing, especially in unheated areas. Texas A&M AgriLife Extension warns that pipes can freeze and burst when outdoor temperatures reach 20°F or lower. Insulate exposed pipes, disconnect garden hoses, and learn where your main water shutoff is. FEMA also recommends keeping the home at 55°F or higher during winter conditions, even when you're away.
Pets: Bring pets indoors during severe cold. Don't leave them outside for extended periods when temperatures are dangerously low.
People: Dress in layers and close off unused rooms if the power goes out. Never run a fuel-burning generator inside a home, garage, or enclosed space. Keep it outdoors at least 20 feet from doors, windows, and other openings to reduce carbon monoxide exposure.
Cold weather can also affect battery performance. Read about how cold weather affects portable power stations before deciding where to store your backup equipment.
A 24-Hour Hard Freeze Checklist
The NWS may issue freeze watches or warnings 24 to 48 hours before the coldest conditions arrive. Use that time to prepare your home and check your backup plan.
When | Task |
Day before | Check your local NWS forecast for "hard freeze" wording in the Freeze Warning |
Day before | Disconnect hoses; cover or bring in tender plants |
Evening | Set thermostat no lower than 55°F |
Evening | Know where the main water shutoff is |
Evening | Test CO detectors near sleeping areas |
If power goes out | Generators outside only, more than 20 ft from windows, doors and vents |
If an outage is likely, follow these winter outage preparation tips to plan for charging phones, powering essential devices, and keeping medical equipment running.
Conclusion
A hard freeze generally means temperatures of 28°F or lower for an extended period, though local weather offices may use different thresholds. Read your local Freeze Warning, protect plants and exposed pipes, and bring pets indoors before the cold sets in. If outages are a concern, plan which devices need backup power and have an electrician check any home circuits that require a special connection. The EcoFlow TITAN 5000 Classic supports selected 120V loads, while the EcoFlow TITAN 5000 also offers 120V/240V output for compatible, professionally connected equipment.
FAQs
What temperature is a hard freeze?
The NWS defines a hard freeze as temperatures of 28°F or lower for an extended period. These conditions can damage sensitive plants and threaten exposed plumbing. However, thresholds can vary by location. For example, NWS Tallahassee uses 25°F.
Is a hard freeze the same as a hard frost?
Not officially. The NWS defines frost and hard freeze separately but doesn't formally define "hard frost." Frost forms when water vapor freezes on cold surfaces, while a hard freeze refers to prolonged low air temperatures. People sometimes use the terms interchangeably.
Does the NWS still issue Hard Freeze Warnings?
No. Since October 2024, the NWS has consolidated Hard Freeze Warnings into Freeze Warnings. These alerts notify people when freezing conditions could damage plants, harm exposed plumbing, or create risks for people without adequate warmth. A warning may still mention a hard freeze when temperatures are forecast to reach 28°F or lower.
How long does a hard freeze have to last?
The NWS glossary describes a hard freeze as lasting for an "extended period" but doesn't specify an exact number of hours. The impact depends on how low temperatures fall and how long they remain there. Local offices may use specific time criteria, so check your local forecast for details.
Will a hard freeze burst my pipes?
It can. Texas A&M AgriLife Extension warns that pipes can freeze and burst when outdoor temperatures reach 20°F or lower. Pipes exposed to the cold or located in unheated spaces, such as garages and crawl spaces, are at greater risk.
For press requests or interview opportunities, reach out to our media team
media.na@ecoflow.com