Digital Thermohygrometer Cornwall Min/Max – Temperature & Humidity Control

The Cornwall Min/Max Digital Thermohygrometer is the fundamental tool that separates a lucky hobbyist from a serious grower, giving you total control over the two most critical environmental factors in your crop: temperature and humidity. Without cables or probes, this all-in-one device provides instant, accurate readings to ensure your plants are thriving, not just surviving.

Are you growing blind when the lights go out? If you don't know exactly how cold it gets at night or how high the humidity spikes when the extraction slows down, you are gambling with your harvest.

Ignoring these fluctuations is the fastest way to ruin a crop. A sudden drop in temperature can stunt growth completely, while invisible humidity spikes are the red carpet for botrytis and powdery mildew. By the time you see the damage on your leaves, it's often too late to fix it.

The Cornwall Min/Max solves this instantly. It doesn't just tell you the current status; it acts as a black box recorder for your grow tents. Thanks to its memory function, you will know exactly the maximum and minimum peaks reached while you were away, allowing you to dial in your ventilation and heating with surgical precision.

Your climate control assistant in a single device

This device is designed to be the eyes of your operation. It continuously scans the environment, measuring temperatures from -30°C to 70°C and humidity levels from 25% to 98%. Its main value lies in the "Min/Max" button: press it to see the extremes reached since the last reset. This is crucial for diagnosing why your plants might be stretching (too hot) or growing slowly (too cold).

Key features and benefits in a nutshell

• Min/Max Memory: Allows you to monitor environmental changes during the dark cycle, giving you the data needed to adjust your Climate Control equipment.
• Large Digital Display: Easy-to-read screen lets you check parameters at a glance without squinting or disturbing the plants.
• Compact & Wireless: Since it has no probe, it's easy to place anywhere; hang it or stand it up without dealing with messy cables.
• Wide Range Accuracy: Covers extreme ranges (-30°C to 70°C), making it durable enough for any grow room condition.
• Battery Efficient: Runs for months on a single battery, ensuring you never lose data mid-grow.

How to use it in a few steps

Getting your environment dialed in shouldn't be complicated. Follow these simple steps to get the most out of your meter:

1. Power Up: Insert the battery (usually included) and the screen will immediately show current temp and humidity.
2. Placement: Place the device at the height of your plant's canopy. Avoid placing it directly under the light bulb or right next to the humidifier for the most accurate average reading.
3. Monitor: Check the display daily. Press the "Max/Min" button to see what happened while you were sleeping.
4. Reset: We recommend resetting the memory (usually by holding the button) at the same time every day, so you track 24-hour cycles accurately.

Frequently Asked Questions

Where is the best place to put the thermohygrometer?

Ideally, place it at the top of the plants (the canopy), where the light hits. However, try to shade the device slightly so the direct radiation doesn't give a falsely high temperature reading. Do not place it directly on the floor.

Does this model have a probe?

No, this is the compact model with built-in sensors. If you need to measure the temperature of the root zone or outside the tent while keeping the display outside, you should look for our Humidity controller and meters section for models with external probes.

How do I reset the memory?

Depending on the specific batch, you usually press the "Reset" button or hold down the "Max/Min" button for a few seconds until the values blink and return to the current reading.

Personal Experience of Pevgrow’s CEO (Alan)

I consider this little gadget the "toothbrush" of growing: it's not the most exciting thing you'll buy, but you absolutely cannot live without it. I keep one in every single drying room and grow tent I manage. It's cheap insurance.

My favorite way to use it is during the first weeks of flowering. I check the "Max" humidity reading every morning. If I see it hit 60% or higher during the night, I know I need to increase my extraction power immediately before mold becomes a threat. It takes the guesswork out of the equation.