In the searing heat on my patio, I’m often reminded of that great song by The Lovin Spoonful; ‘Hot town, summer in the city, back of my neck gettin’ dirt and gritty’. It’s a classic tune with great lyrics – and it captures those hot, summer days really well. 

It’s often impossible to tell how hot it’s getting in your backyard, but it’s important for avoiding sunburn and sunstroke when you’re relaxing on the lounger. This is where a patio thermometer comes into its own, so you can put the awning up or retreat into the shade if things get just too hot.

If you’re considering buying an outdoor thermometer, we’ve put together some key facts and information in this article to help you make an informed decision when parting with your hard earned cash.

How Do You Measure Outdoor Temperature?

If you are proud weather nerds, like us – the more weather information, the better. If you are considering a patio thermometer, read on before you buy.

Plain or decorative, classy, or colorful, there are lots of outdoor thermometer choices. Do you want to read the outdoor temperature inside or outside? Do you prefer a big retro dial or a colorful indoor digital display? Are you only interested in knowing the temperature or would you like more weather information, like humidity? Would you like to be warned about weather events in your neighborhood?

Outdoor thermometers measure the ambient (or atmospheric air) temperature. Because they measure air temperature, they need plenty of air all around for the most accurate readings. Outdoor thermometers can be analog or digital.

Analog thermometers use thermosensitive liquids or metals. Analog thermometers have glass tubes filled with bright-colored liquids, or mercury, and have degrees marked along the side. Bimetal, or dial, thermometers are big and round and have a needle pointing to the temperature.

Digital thermometers can be direct reading – you read the display through your window – or remote reading. Remote reading thermometers can transmit the outside temperature to you, standing inside. Sensor ranges vary but can be up to several hundred feet.

Weather stations show you more than just temperature: sensors read humidity and barometric pressure. They inform you on the phase of the moon and give helpful suggestions for how to dress outside. 

They have memory, so you can see what the nighttime low was. Weather stations can check for weather information for your area, like watches or warnings.

How Does An Outdoor Thermometer Work?

Outdoor thermometers measure the temperature of a gas – the air. To do so, they need to be in a spot where gas molecules flow freely around them. Analog choices are liquid, like mercury or red alcohol, or digital.

Mercury thermometers are a type of analog thermometer. They have a small glass rod with a bulb at the bottom. The bulb is filled with nitrogen gas and a liquid: either mercury or a red-colored alcohol. Increasing air temperature causes the liquid in the bulb to expand. When it expands, it flows up the glass tube. The glass tube has been calibrated and is marked with degrees, either Fahrenheit or Celsius (or both).

Mercury thermometers are easy to read and very accurate. But mercury is poisonous. In fact, selling mercury thermometers is banned in some states. It poses a danger in your house and should not go into landfills. Red alcohol is often used instead of mercury, and although it’s much safer, the thermometer is less accurate.

Bimetal – or dial – thermometers are another analog type. They are big and round with a needle pointing to the temperature degrees. Dial thermometers date back to 1759 and are commonly found in the kitchen and on BBQ lids.

They are called bimetal thermometers because the mechanism consists of two metals bonded together and coiled. The metals respond to temperature differently. The bimetal coil is fixed at one end to a needle that moves, pointing to the calibrated temperature. 

Digital thermometers work using the electrical property called resistance. Resistance is the measurement of how difficult it is for an electrical current to flow through an object. Most digital thermometers use a type of resistor called a thermistor.

Resistors measure the amount of opposition an electrical current has. As the temperature changes, the resistance changes. The thermistor measures the changes. The strength of the resistance can be calibrated to temperature. 

For more information on how thermometers work, try this website.

What’s An Outdoor Thermometer Called?

Analog thermometers that don’t have remote capabilities are often referred to as “wall thermometers”.

Thermometers with sensors that have remote wireless capability are called “indoor/outdoor” thermometers.

How Accurate is An Outdoor Thermometer?

Mercury thermometers are super retro and filled with a toxic material – but they are world-class accurate. Once calibrated, mercury thermometers will be accurate for a decade, even a century. 

Mercury thermometers are accurate from one-tenth to two-tenths of a degree. In fact, they are more accurate than the eyeballs reading the temperature.

Dial and digital thermometers are accurate to plus or minus 2 degrees. When you buy them, they will be well calibrated, but gradually the thermometer will lose calibration. Digital and dial thermometers should be calibrated once every year, particularly if your climate has extremes.

How Do You Calibrate An Outdoor Thermometer?

Most digital and dial thermometers are factory calibrated, but they will need recalibration after a year or so. Be sure to check the specifications before you buy, though, because some models don’t come with a calibration feature. 

For models that allow calibration, check the instructions first. Experts suggest bringing the outdoor thermometer inside and testing it against known temperature points, like the freezing point of water. Or, if you have a new, calibrated, indoor temperature gauge reading, adjust it to that.

The easiest calibration is to the temperature of freezing water, 32° F. Fill a glass with half ice and half water and let it sit for up to 15 minutes. Then, put the thermometer’s probe in the glass, at least one inch. It should read 32°F or 0° C. Adjust the temperature on your dial or digital thermometer with the calibration control to that exact temperature.

Worst case scenario, if your thermometer doesn’t allow for calibration – you’ll know to add or subtract the degrees from the test.

Where is The Best Place For An Outdoor Thermometer?

The National Weather Service says the best place to put your outdoor thermometer is in a shady spot around 5 feet off the ground (the “Goldilocks” zone). 

Thermometers will give you a more accurate temperature if they have air flowing around them. The more open a spot, the better. Even though it’s handy, putting a thermometer in a window up against the side of your house is not the best spot. Consider buying a bracket to get the thermometer away from the solid wall.

Try to find a shady spot for the thermometer. Full sun will not give an accurate temperature (too high), plus your thermometer will last longer with a little protection. 

A concrete patio or concrete pavers attract more heat than grass. In fact, concrete attracts so much heat that the National Weather Service recommends that outdoor thermometers be placed 100 feet away from a large concrete slab.

If you have the option, place the thermometer in a shady spot over a lawn or garden bed. Experts recommend the north side of the house. Here’s a video to help you place your thermometer.

Are Outdoor Temperatures Measured in Sun or Shade?

“Shade temperature” is the true air temperature. When your thermometer is in the sunshine, the measurement is of the heat energy of sunshine, not the true air temperature.

How Much is An Outdoor Thermometer?

The cost of a simple, single purpose analog outdoor thermometers starts at $8. A digital, remote reading thermometer starts at $20. 

For weather junkies, there is a large range of weather stations. At the low end, a weather station can cost $40. High end home weather stations have sensors for temperature, barometric pressure, humidity, UV radiation, rain, and wind gauges. They have WIFI capabilities, allowing you to check the station remotely. It will check online for weather alerts. Many of these are under $200.

Which Outdoor Thermometer Brands Are Best?

There are many brands of outdoor thermometers. Here are some that are consistently in the “Best” lists.

• AcuRite. Founded in 1943, their focus is hyper-local weather monitoring. They make products for the outdoors and smart devices for the inside. Their products are accurate and scientific. They have excellent support.
• Ambient Weather. Ambient Weather manufactures weather stations, environmental monitoring, and home monitoring sensors. Ambient Weather was founded in 1998 in Arizona. One of their services offered with a weather station purchase is a connection with a network of Ambient Weather stations.
• La Crosse Technology offers a wide range of analog and digital thermometers, and weather stations. Their products are well reviewed, and they offer product support. La Crosse was founded in 1983 in Wisconsin. Sales, distribution, and customer service are all located in La Crosse, Wisconsin.
• Taylor Precision Products makes precision products for the kitchen, bathroom, and backyard. They manufacture bath scales, food, and weather thermometers. Taylor was founded in 1851 in Illinois.
• Thermapro makes a wide range of temperature products, from the kitchen to the backyard. Thermapro was started in 2014. They have excellent customer service and warranty coverage.

Conclusion: Where Can I Buy An Outdoor Thermometer?

In addition to big box hardware stores and garden centers, outdoor thermometers are offered online.

You can find them on Amazon, Lowes and Home Depot (amongst others), and get them delivered direct to your door.

So when you next find your temperature rising out on the decking or patio, you’ll know exactly how hot ‘hot’ really is.

That’s it from me – I’ve still got ‘Summer in The City’ going round in my head so I’m off to find my old vinyl records. 🙂