7 Best Frost Alarms That Save Sensitive Plants

Frost can wipe out months of careful cultivation in a single night. Sensitive plants like tomatoes, peppers, and citrus need early warning when temperatures drop toward freezing. The right frost alarm gives you time to protect your investment with covers, heat sources, or temporary shelters.

Disclosure: As an Amazon Associate, this site earns from qualifying purchases. Thank you!

1. La Crosse Alerts Mobile 926-25101-WP Temperature & Humidity Alert System

This weatherproof system stands out for hobby farmers juggling multiple growing spaces. You get instant alerts through WiFi connectivity when temperature or humidity falls outside your custom thresholds.

The base station connects to your home network and pairs with up to eight wireless sensors. Each sensor has a 400-foot range in open space, typically enough to cover most hobby farm layouts from greenhouse to high tunnel to outdoor beds.

Key Features and Connectivity

The system sends push notifications, texts, and emails simultaneously when temperature drops into danger zones. You can set different thresholds for each sensor location, which matters because your greenhouse, cold frame, and outdoor plantings don’t all need the same trigger point.

The sensors are IP65 rated for weather resistance. They’ll handle rain, snow, and humidity without protective housing. Battery life runs about two years on three AAA batteries per sensor.

Data logging tracks conditions over time through the La Crosse View app. You can spot patterns in how quickly different areas cool down after sunset, which helps you predict where frost damage is most likely to strike first.

Best For Hobby Farmers With Multiple Growing Areas

This system makes sense when you’re managing several microclimates across your property. If you’re protecting seedlings in a garage, winter greens in a hoop house, and potted citrus in a shed, the multi-sensor approach saves you from checking each space manually.

The subscription-free cloud platform keeps your historical data accessible without monthly fees. That’s a real advantage over some competitors that lock features behind paywalls.

One consideration: the WiFi dependency means you need reliable home network coverage where you place the base station. If your router is in the house and your greenhouse is 200 feet away, you might need a WiFi extender to maintain stable connectivity.

2. SensorPush HT.w Wireless Water-Resistant Temperature & Humidity Smart Sensor

The SensorPush HT.w bridges the gap between basic monitoring and professional-grade systems. It uses Bluetooth connectivity through a separate WiFi gateway, creating a reliable alert system without requiring each sensor to connect directly to your network.

The sensor itself is compact, about the size of a matchbox, and completely water-resistant. You can place it directly among your plants without worrying about condensation or irrigation spray damaging the electronics.

Why It’s Ideal for Greenhouses and Cold Frames

Greenhouses create challenging monitoring environments with high humidity, temperature swings, and condensation. The HT.w handles these conditions better than many WiFi-direct sensors that struggle with moisture interference.

The Bluetooth-to-WiFi architecture also solves a common hobby farm problem: structures with metal frames or thick coverings that block WiFi signals. You place the small WiFi gateway within Bluetooth range (up to 325 feet in open space), and it relays data to your phone from there.

Accuracy is ±2°F for temperature and ±4.5% for humidity. That precision matters when you’re working in the narrow window between optimal growing conditions and frost damage.

App Integration and Alert Customization

The SensorPush app lets you set high and low alerts for both temperature and humidity. You can adjust sensitivity, triggering alerts immediately when thresholds are crossed or waiting to confirm the reading for several minutes to avoid false alarms from temporary fluctuations.

Unlimited data storage in the cloud means you can analyze seasonal patterns. Look back at last spring’s late frost to see exactly when temperatures dropped and how long they stayed in the danger zone.

The system supports unlimited sensors on one account. Add sensors as your operation expands without buying new base stations or subscriptions. Each sensor runs about a year on one CR2477 coin battery.

3. Temp Stick Remote WiFi Temperature & Humidity Sensor

The Temp Stick works anywhere cellular service reaches, making it the go-to choice for off-grid growing areas. It connects directly to WiFi without needing a base station, and the cloud platform alerts you through cellular networks even when your home internet is down.

This sensor was designed for remote monitoring, vacation homes, RVs, and similar applications, which translates perfectly to hobby farm outbuildings and distant growing spaces.

Unlimited Range and Cloud-Based Monitoring

As long as the Temp Stick can reach a WiFi network, you’ll get alerts anywhere you have cell service or internet access. That’s genuinely unlimited range in practical terms.

Set up is straightforward through the mobile app. The device connects to your 2.4GHz WiFi network and begins reporting temperature and humidity every minute. Data streams to the cloud automatically.

Alerts come via text, email, or push notification when readings cross your custom thresholds. The system checks conditions continuously, so you get warnings within a couple minutes of temperature changes, usually enough time to take protective action if you’re on the property.

Battery Life and Durability

TwoAA batteries power the unit for 12-24 months depending on WiFi signal strength and reporting frequency. Weaker WiFi signals drain batteries faster as the device works harder to maintain connection.

The housing is sealed against moisture but not fully submersible. It handles greenhouse humidity and occasional rain without issues, but shouldn’t sit in standing water.

One drawback: the subscription-free service requires one-time purchase, but you’re limited to alerts for one phone number and one email per device. Additional notification contacts require additional sensors or workarounds through email forwarding.

4. AcuRite 06002M Wireless Indoor/Outdoor Temperature and Humidity Sensor

Sometimes you just need simple, reliable frost monitoring without app integration or cloud connectivity. The AcuRite 06002M delivers exactly that at a fraction of the price of WiFi-enabled systems.

This is a traditional wireless weather station with a remote sensor and a display console. The sensor transmits temperature and humidity readings to the console every 18 seconds using a 433MHz signal with a 330-foot range.

Budget-Friendly Option for Small Operations

The console lets you set high and low temperature alarms with audible alerts. When the temperature at the sensor drops below your set point, the console beeps until you acknowledge it.

That audible-only alert system is both the strength and limitation of this approach. You need to be within earshot of the console, typically inside your house, to hear the alarm. It won’t text you if you’re away from the property.

But for many hobby farmers, that’s perfectly adequate. If you’re home most evenings during frost season and your console is on the kitchen counter or bedroom nightstand, you’ll hear the alert in time to cover plants or fire up supplemental heat.

The system handles up to three remote sensors, letting you monitor multiple areas. The console displays all three locations and cycles through them every few seconds.

Sensors run on two AA batteries for about two years. The console uses two AA batteries or an optional AC adapter. Total investment is usually under $50 for console and sensor.

Consider this option if you’re protecting a single greenhouse or garden area close to your house, want reliable alerts during sleeping hours, and don’t need remote access when you’re away.

5. Govee WiFi Temperature Humidity Monitor H5179

The Govee H5179 brings smart home integration to frost protection at a competitive price point. It connects directly to 2.4GHz WiFi networks and pairs with Alexa, Google Assistant, and IFTTT for automation possibilities.

The sensor logs data every two seconds and uploads to the Govee cloud platform for real-time monitoring through the smartphone app. Response time is impressively quick, alerts typically arrive within 30-60 seconds of threshold breaches.

Smart Notifications and Data Logging

Set custom temperature and humidity ranges in the app, and receive push notifications immediately when readings move outside those boundaries. The app lets you configure different alert schedules, more sensitive overnight when frost risk is highest, less aggressive during afternoon when temperatures naturally rise.

Data logging stores two years of historical information in 10-minute intervals. Export data as CSV files to analyze patterns in Excel or similar spreadsheet programs.

The display screen on the unit itself shows current readings, though you’ll likely check the app more often than physically visiting the sensor. A smiley-face icon indicates comfort levels, a nice touch that’s not particularly useful for frost monitoring but shows the consumer electronics origins of this product.

Integration With Smart Home Systems

IFTTT integration opens up interesting automation possibilities. Trigger smart plugs to turn on space heaters when temperature drops, activate lights as visual alerts, or log conditions to Google Sheets automatically.

Alexa and Google Assistant integration means you can ask about current temperature verbally without opening the app. “Alexa, what’s the greenhouse temperature?” gives you instant information when you’re working with dirty hands.

The sensor is compact and includes a mounting hole for easy placement. It’s not weatherproof, only water-resistant enough for high humidity environments. Keep it out of direct rain or irrigation spray.

Battery life is the main weakness. The rechargeable lithium battery lasts about 2-3 months between charges via USB-C cable. That’s significantly shorter than sensor replaceable batteries, requiring more frequent attention during busy growing seasons.

6. Inkbird IBS-TH2 Plus Bluetooth Temperature and Humidity Sensor

The Inkbird IBS-TH2 Plus takes a Bluetooth-only approach, which sounds limiting until you understand the use case it’s designed for. This sensor excels when your frost-sensitive plants are within 150 feet of where you spend your evenings.

No WiFi networks, no cloud platforms, no subscription possibilities, just direct Bluetooth connection between sensor and phone. The simplicity reduces points of failure and keeps costs low.

Reliable Performance for Localized Monitoring

The sensor broadcasts continuously via Bluetooth, and the Inkbird app connects whenever your phone is in range. Set temperature and humidity alerts in the app, and you’ll receive notifications as long as you maintain Bluetooth connection.

This works well for hobby farmers whose living space is near their greenhouse or growing area. Sit in your living room on a March evening, and you’ll get alerted when the greenhouse drops toward freezing. Walk out to the property perimeter where you might lose connection, and alerts pause until you’re back in range.

The sensor is IP65 waterproof rated and handles outdoor placement in weather-protected areas. Temperature accuracy is ±0.9°F and humidity accuracy is ±3% RH, among the most precise in this price range.

Data logging stores up to 30 days of readings directly on the sensor with 10-second intervals. When you reconnect to the sensor after being out of range, the app syncs and displays all missed data points.

Two AAA batteries power the unit for about six months. Battery life varies based on reporting frequency, you can adjust from every 10 seconds to every hour to extend operation between changes.

The limitation is obvious: if you’re away from the property overnight or for extended periods during frost season, this sensor won’t reach you. But as a budget-conscious, high-accuracy option for monitoring spaces near where you live and sleep, it’s hard to beat.

7. MarCELL Cellular Temperature and Power Monitor

The MarCELL device solves the problem of rural properties without reliable WiFi coverage in growing areas. It uses cellular connectivity, specifically Verizon’s network, to send alerts, making it functional anywhere you have cell signal.

This isn’t technically a WiFi sensor at all. It’s a cellular monitoring device with temperature sensing, power monitoring, and water detection capabilities built into one unit.

Cellular Connectivity for Remote Farm Locations

The MarCELL contains its own cellular modem with an included SIM card. It connects to Verizon’s network without requiring your phone plan or creating hotspot drain on your devices.

Setup involves plugging in the unit, creating an account, and setting your alert parameters through the web portal or mobile app. The device reports conditions every 15 minutes and sends immediate alerts when thresholds are breached.

Alerts arrive via text, email, or phone call, yes, actual voice calls that will wake you at 2 AM when frost threatens. You can configure which alert types you want for which conditions.

The temperature sensor reads from -40°F to 257°F with ±2°F accuracy. That range handles everything from severe cold snaps to heat monitoring in summer growing conditions.

Power Outage Detection Feature

The built-in power monitor alerts you if electricity fails in your growing space. That’s crucial for hobby farmers relying on electric heaters, grow lights, or ventilation fans to protect sensitive plants.

The device has a backup battery that keeps it reporting for several hours during power outages, so you’ll know immediately when electricity fails and can respond before temperatures drop dangerously.

Optional accessories include external temperature probes for monitoring multiple locations from one device and water sensors for flood detection in growing areas.

The catch: MarCELL requires a monthly subscription for cellular service, typically $10-15 per month depending on plan. That ongoing cost adds up compared to WiFi-based systems, but it’s worthwhile if cellular is your only reliable connectivity option in remote growing areas.

Consider this option for off-grid high tunnels, remote orchards, or any growing space where WiFi isn’t practical but cell signal reaches. The power monitoring feature adds extra protection for climate-controlled spaces that depend on electrical systems.

Frequently Asked Questions

What is a frost alarm and why do I need one for my plants?

A frost alarm is a temperature monitoring device that alerts you when temperatures drop toward freezing. It gives you time to protect sensitive plants like tomatoes, peppers, and citrus with covers, heat sources, or shelters before frost damage occurs.

How do frost alarms send alerts when temperatures drop?

Frost alarms send alerts through various methods including push notifications, text messages, emails, or audible alarms. WiFi-enabled models use smartphone apps, while cellular devices can send voice calls, and basic systems use audible beeps on display consoles.

What’s the best frost alarm for hobby farmers with multiple growing areas?

The La Crosse Alerts Mobile 926-25101-WP is ideal for multiple growing areas, supporting up to eight wireless sensors with 400-foot range. You can set different temperature thresholds for each location like greenhouses, cold frames, and outdoor beds.

Do frost alarms work without WiFi or internet connection?

Yes, several options work without WiFi. The MarCELL uses cellular connectivity via Verizon’s network, the Inkbird IBS-TH2 Plus uses Bluetooth, and the AcuRite 06002M uses traditional wireless signals with an audible alarm console.

How accurate are frost alarms for temperature monitoring?

Most quality frost alarms offer accuracy between ±0.9°F to ±2°F. The Inkbird IBS-TH2 Plus provides the highest precision at ±0.9°F, while devices like SensorPush and MarCELL offer ±2°F accuracy, sufficient for frost protection.

Can I integrate frost alarms with my smart home system?

Yes, the Govee H5179 integrates with Alexa, Google Assistant, and IFTTT, allowing automation like triggering smart plugs to activate space heaters when temperatures drop or setting up voice-activated temperature checks for your greenhouse.