Part II: Effective, “Low Tech” Method To Verify Humidor Temperature

Editor’s Note: This is not a paid endorsement of or a solicitation for any of the products mentioned in this article and 99 Cigars neither sought nor received compensation from any brand whose products are mentioned or featured.

As I mentioned in Part I of our foray into effective means of calibrating our hygrometers, the most challenging aspect of safeguarding our precious cigars is keeping them in an ideal environment, an environment in which the proper temperature and humidity, or Relative Humidity, are critical for their care and feeding. Achieving your ideal humidity, while critical, is only part of the equation. Temperature surveillance and the accuracy with which your thermostats function is equally vital.

This article focuses on providing information on an easy, effective way of accurately measuring temperatures and calibrating existing thermometers. This is not a comparo of various thermometer technologies/products nor general advice on maintaining cigars in a given humidor. In addition, the following information is meant to be a helpful guide to even the most casual of smokers, not an exhaustive scientific exposé or exercise, e.g. “paralysis by analysis.”


If you have or are thinking of purchasing a humidor for the first time and it is either an “ambient” (non-electronically controlled)  or an electronically controlled model (one that automatically modulates the desired temperature), how are/will you measure the temperature(s)? Home thermostat? Analog or digital thermometer? Oral thermometer? A better question is, “how accurate IS your thermometer?” What we have learned over the years about storing cigars is that the majority of thermometers, even the more popular digital units, are inaccurate to some degree. Some as much as almost 5° F, on the high side. So, unless you’re willing to pony up mucho dinero to get the latest and greatest in digital thermostat technology, which is understandable if you’re aging thousands of dollars in rare cigars, there’s a more reasonable and economic means to keep track of your stogey’s temperature. And you can keep whatever style thermostat you like. But first, lets take a quick look at the challenges we all face.

Those with “ambient” humidors, i.e. those that sit in our homes, at the mercy of ambient temperatures of the respective room in which they are stored, face the toughest challenges in maintaining temperature and humidity. Rarely is the air temp throughout your home equal in every space, particularly during extreme winters and summers. Further, the temperature in any particular room can fluctuate up to and even past +/-5° F depending on multiple factors. For example, our office is in South Texas and during the dog days of summer, at a general A/C setting of 75° F, the temperature in our shaded office fluctuates between 73° and 77° F over a 24 hour period. And let’s face it, even though we recognize the ideal temperature for storing cigars is around 67-69° F, we can’t very well crank down the A/C thereby turning our spaces into a meat locker.

If you’re one of the lucky ones that have moved to an electronic humidor or “coolidor” that maintains a set temperature, I’m sad to say you’re not out of the woods when it comes to similar factors affecting what you thought was a sealed, electronically-controlled environment. Changes in ambient temperature and other factors can also negatively impact the temperature inside what you thought was an automated system. For example, we have two Newair 300 systems with a temp control system. As the air warms in our office, it requires the Newair system to adjust the air temp down in order to compensate. This means the system thermostat is often off by 1-2° F  during the hottest part of the day and we have to adjust manually.

REMEMBER: As the temperature in our humidors creep upward, the relative humidity (RH) begins to decrease and vice versa so a stable environment with minimal fluctuations is what we should shoot for. 


The most common thermometers used in our humidors are either analog or digital and they’re typically compact in size. The most popular technology seems to be digital thermometers/hygrometers like the Cigar Oasis (formerly Western Humidor) Caliber IV pictured above. The pros of the digital thermometer are size, relative cost, long battery life and overall accuracy. But differences in the way the temperature is measured can lead to a range of inaccuracies.

In general, digital thermometers rely one of four common types of sensor technology which must first convert an analog input, e.g. voltage, resistance, etc., by passing this info on to a converter which converts the signal to a series of pulses which becomes the digital output. Without going into details, it’s important to understand that each stage in this process is prone to inaccuracies as the signals are passed from the analog to digital world. Thus, due to a variety of factors,  these fluctuations can and will lead to a range of inaccurate readings. If you’d like to learn more about the nuts and bolts of digital thermometer technologies, check out the downloads by Tegam and Texas Instruments.

REMEMBER: Tobacco beetle larvae hatch in the area of 75° F so don’t unwittingly lay out the welcome mat to what could be a smorgasbord for these destructive critters.


Striving for, achieving and maintaining a desired temperature is one thing, knowing  the actual value is a different matter. Read the product insert of most digital thermometers and it’ll claim temperature accuracy to within +/- 1° or 2° F. The reality is while this may be true most of the time, it can drift further. In contrast to the ever evolving “high tech” digital technologies available today, keeping these devices honest while also giving you a more accurate representation of your temperature, wherever that may be, can be done cheaply and through a largely forgotten “low tech” means: the glass thermometer.

Before IR and digital thermometers arrived, you probably got a mercury-filled glass thermometer shoved into your armpit or under your tongue if you were unfortunate enough to land at the school nurse’s office. The fact is, glass thermometers never went away and in fact have become, in some applications, the gold standard for measuring temperature. The livelihoods of sectors like chemical and biological sciences, food manufacturing or even brewing, depend in large part on the accredited accuracy of the venerable glass thermometer.

Glass Mercury Scientific Thermometer

As a former biological scientist, we closely monitored the temperatures of our freezers, refrigerators, incubators and our labs using glass thermometers. The most common type of these thermometers is the “verification thermometer” which is a glass thermometer  inserted through the cap of a short bottle with its bulb submerged in an alcohol-based solution. The alcohol’s low freezing point made it necessary for our cold appliances. So, in essence the thermometer was measuring the temperature of the solution in the jar. The reason for this strategy is two-fold: to utilize a known substance that could be measured and compared to an accepted standard and the resulting high degree of accuracy.


The organization that governs and maintains these and numerous other standards is the National Institutes of  Standards and Traceability, or NIST. Having this type of accreditation behind it makes this simple technology highly robust and accurate, often to within +/- 0.5-1.0° Celcius (C), which is an even more sensitive and precise measurement over that of Fahrenheit. By the way, for every increase in 1° F is equal to ~0.5555° C. Even better is the fact that most manufacturers of these products have validated use of thermometers with safe, non-toxic liquids in place of both mercury and alcohol. This makes it ideal  for use in our homes and electronically controlled humidors.

H-B Frio-Temo Verification Thermometer

We’ve employed several of these throughout our office and in our Newair Humidor systems to measure both ambient and humidor temperature giving us a firm foundation and reassurance this is within the expected +/- 0.5° C. As a bonus we can compare the readouts of our digital and thermostatic devices, thus allowing us to calibrate them, up or down, with known differences for which to allow. To be clear, you cannot calibrate temperature by manipulating the actual digital thermostat in most cases, so you would simply note (like we did for RH in Part I) the difference on the back of the device or in a log of some kind. So, please DON’T toss your existing temp devices!

Unfortunately, these little wonders aren’t “little” (about 7″ tall) enough to fit in most desktop humidors, but it doesn’t matter because they’re subjected to ambient air, so placing them next to or in the vicinity of your humidor is fine. Each verification thermometer comes with it’s own specific serial number and official NIST Statement of Accuracy and Traceability and are reportedly good for one year. You can expect retail costs of these to range from $50-$60 and they are available at Amazon…of course! You can obtain them in either Celsius or Fahrenheit measurements and you can even choose the model whose temp verification range is close to where you want to be, e.g. the model we purchased measures between 15° – 50° C or 59° – 122° F, so this is ideal for humidors.

Can you get state-of-the-art digital devices with maximum temperature measurement accuracy ? If money is no object, of course you can! Personally I think the ~$23 for a typical digital hygrometer/thermometer and ~$53 for a verification thermometer is money well spent and in the end, is all the insurance you, and your cigar collection, need. – In Fumo Pax!

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