Expert Contributor:
Julia Nowak
You’re glassing a field on a calm night when everything looks sharp: heat signatures pop, movement is easy to pick up. Then the weather shifts. Fog rolls in, humidity spikes, or a light rain cools the ground, and suddenly the image flattens. Outlines soften. Distances feel shorter. Animals that were clear a minute ago now blend into the background.
This isn’t your device malfunctioning; it’s the atmosphere reshaping the infrared signal long before it reaches your sensor. Fog, rain, snow, and heat all change how much IR energy travels through the air and how much contrast exists between your target and its surroundings.
The good news? Once you understand how each condition affects thermal performance, you can adapt your tactics. Additionally, with a high-sensitivity Pulsar optic, you stay effective even when the weather works against you.
Weather affects thermal imaging in two ways: it changes how much infrared energy reaches your device and how much contrast remains between an animal and the background. When either of these drops, the image loses clarity.
In moisture and heat, expect reduced detail. You can maintain reliable spotting by scanning more slowly, choosing shorter lanes, focusing on shaded or transitional terrain, and using a high-sensitivity thermal system designed to preserve contrast in challenging weather.

Picture taken with Merger LRF XP50 by Julia Nowak in thick fog. With her naked eye, she could barely see objects 20-30 meters away.
Yes. Thermal devices detect infrared radiation in the LWIR band, which normally travels through the atmosphere with very little loss. This is because LWIR aligns with the atmospheric transmission window, allowing clear, high-contrast imaging on dry, stable nights.
Weather disrupts this advantage. Humidity, fog, and rain introduce water vapor and droplets, narrowing this transmission window. As these elements increase, less infrared energy reaches the sensor, and both thermal contrast and effective range decrease.
Hunters notice this most clearly in detection, recognition, and identification distances. For example:
Background temperature adds another challenge. Rain-cooled surfaces and summer heat push the environment toward thermal equalization, shrinking the temperature delta between the animal and its surroundings. Even when detection is still possible, recognition and identification become slower and less reliable.
High-end Pulsar devices help counter these effects. A sensor with low sNETD, such as <25 mK or even <18 mK, can separate extremely small heat gradients, preserving micro-contrast when absorption and humidity work against long-range visibility.
Read more: How does weather affect our hunts?
All weather effects ultimately influence how infrared energy in the LWIR band travels from the animal to your device. Anything that absorbs, scatters, or equalizes heat reduces what the thermal can display. These mechanisms determine how far you can detect an animal and whether you can recognize or identify it with confidence.
In an ideal world, you would probably want to have different devices to battle different obstacles. But in reality, that’s hardly accessible to most of us. That’s why our expert hunter Julia Nowak recommends playing around with settings:
It can differ from hunter to hunter, but I like to play with different settings, colour paletes, brightness, contrast etc., depending on the weather conditions outside. And that is what mostly helps me to see “a bit better” in challenging circumstances. For example, my favourite for humid and foggy night is a Black Hot with very high contrast. But I recomennd everyone to test what works best for them.
Absorption occurs when humidity or fog droplets absorb part of the infrared signal. The higher the moisture concentration, the less energy reaches the sensor.
Rain, mist, and blowing snow scatter infrared energy by redirecting it away from the sensor.
When the background temperature approaches the animal’s temperature, the temperature delta collapses.
Read more: The operating principles of thermal imagers
Light fog is usually manageable, but as fog thickens, water droplets absorb and diffuse more infrared energy. This attenuation reduces detection range, softens outlines, and lifts the brightness of the entire scene. In dense fog, large animals may appear as faint, low-contrast shapes because much of their emitted heat never reaches the sensor.
Fog alters the scene in predictable ways, helping hunters understand when to adjust their expectations.
Taking weather into account is also very important if you’re testing out a device in the field before buying it. Julia explains why:
I often catch people who have compared some devices in totally different weather conditions complaining later about the one they used in extreme weather to the one they used during a nice, chill evening… So I think that the most important in general is to be aware that any device will not work as good in difficult weather conditions as it can perform when the weather outside is perfect… Our own eyes also have trouble to see well in the fog and so can be a thermal device (which will still help us to see more even then!).
With that being said, I have tested the settings I mentioned before it in a very dense fog, when I couldn’t see a tree 50m away from me with my own eyes, but I was still able to easily get quite sharp image of animals at 300-400m through thermals.
Because fog limits both clarity and range, it helps to adjust scanning technique to what the atmosphere allows.
These small adjustments help maintain reliable spotting as fog alters the infrared landscape.
Read more: How thermal scopes work
Rain and humidity reduce thermal contrast because droplets and vapor absorb part of the infrared signal before it reaches the sensor. Wet ground and vegetation cool quickly, narrowing the temperature difference between animals and the background. The result is a softer image with shorter recognition and identification distances, especially in thick vegetation where moisture collects.
Humidity alone can have the same effect. In coastal air, marshes, or windless nights with high saturation, long-range visibility drops even without visible rain. High-sensitivity Pulsar sensors help preserve micro-contrast in these conditions, but no device can fully overcome the physics of moisture-laden air.
Rain does not impact thermal imaging uniformly. The density and intensity of precipitation directly affect atmospheric transmission and scene clarity.
For Julia, rain definitely poses more challenge than the fog:
I think rain is more challenging in general. It is not just about the sensor’s performance, but everything around… from practical point of view. It is loud, so you cannot rely on that sense too much. Everything gets wet, so you have to make sure your lenses stay dry, otherwise it will also affect what you see. And I also have a feeling that drops of rain consistently falling are fooling eyes more, as the IR signal gets interrupted again and again, which is different to looking through a “curtain” of fog.
The heavier the rain, the more the IR signal breaks down before reaching the device. Even high-end sensors must work harder to interpret the incomplete information that reaches them.
To remain effective in wet conditions, hunters can make tactical adjustments that complement how thermal systems interpret the environment.
These tactics help maintain detection confidence even when rain weakens the IR signal.
Snow affects thermal visibility in two distinct ways. Falling snow introduces small airborne particles that scatter infrared energy and slightly reduce clarity, especially at longer distances. The bigger effect, however, comes from snow-covered ground. A cold, uniform surface creates a strong contrast that makes warm animals stand out clearly.
This advantage can diminish when windchill cools exposed fur or when wet snow clings to an animal’s coat and masks body heat. In those moments, animals remain detectable, but outlines and species-defining details become harder to interpret.
Snow often improves the hunting view, especially when the snow layer is cold, dry, and uniform.
Not all snow improves imaging. Several scenarios introduce noise and reduce clarity.
To stay effective in snowy conditions, hunters can adjust scanning technique, timing, and positioning.
These adjustments help maintain dependable detection and recognition when winter conditions reshape the infrared landscape.
Read More: How do seasons affect the use of thermal?
Heat reduces thermal visibility because ground, rocks, and vegetation absorb solar loading throughout the day. As this background warming increases, temperatures approach those of the animals you are trying to detect. When that temperature gap narrows, contrast collapse occurs, and the scene looks “flat,” especially in midday or early evening when surfaces still radiate stored heat.
Animals remain detectable, but fine edges, shape, and posture become harder to interpret because the device receives less usable temperature separation.
Thermal crossover is a brief period in the diurnal cycle when background temperature and animal temperature match. It happens around sunrise and shortly after sunset. During these windows:
Recognizing these predictable low-contrast periods helps hunters plan their scans more efficiently.
A safety note from Julia:
Safety always goes first – it can never be about guessing while hunting. It is important to be aware of the capabilities of our equipment depending on the conditions and we need to adapt to it. We need to be 100% sure about the target before taking any hunting decision.
And yes, sometimes if you forget to consider the conditions around you… you can end up sneaking for few hundred meters on a wildboar-like looking stone!
Summer hunting requires choosing locations and scanning patterns that protect the sensor from the worst effects of heat.
These adjustments improve reliability during the hottest parts of the season, when thermal contrast is naturally at its lowest.
In moisture and heat, NETD and lens aperture (F-number) influence real-world performance far more than maximum magnification. Moisture absorbs and scatters IR energy, and hot ground reduces the temperature gap between game and background. In these conditions, a thermal’s ability to detect very small temperature differences depends on the quality of its microbolometer and its ability to draw in IR energy through a fast objective lens.
Magnification cannot restore detail lost to low contrast; it only enlarges it. What matters is how much infrared signal reaches the sensor and how finely that signal can be separated from background noise.
Read more: What defines thermal image quality
NETD measures the smallest temperature differential a thermal sensor can detect. Lower NETD means better visibility when fog, humidity, or heat compresses temperature separation. A sensitive sensor preserves:
This is why NETD becomes the defining metric whenever weather reduces contrast. And while it’s hard to define a recommended base number, we still asked Julia for her take:
This is a bit tricky question and really depends on specific situation and conditions… Sometimes – in a weak rain or light fog even 35 mK can still manage rather OK, but sometimes we need the 25 or lower. But for sure bad weather is when we will much easier notice the differences between different NETDs capabilities.
Note: In the quote above, Julia talks about the raw NETD, unadjusted for the software algorithms. Please note that some manufacturers will provide their NETD only after algorithms are applied, resulting in lower, albeit not as precise numbers. For ease of comparison and transparency, Pulsar provides both numbers.
Read more: NETD, sNETD, and beyond: everything you need to know
Pixel pitch determines how the microbolometer resolves fine structure.
Resolution and pixel pitch together dictate how much detail survives at longer distances, especially when temperature differences are small.
Pulsar devices combine low-NETD sensors with fast lenses and refined image processing to stay effective in poor weather. For example:
These system-level advantages help maintain recognition and identification capability when weather conditions degrade raw IR input.
Pulsar thermal imaging maintains effectiveness in fog, rain, snow, and heat because performance depends on the entire system, not a single specification.
When atmospheric attenuation reduces the LWIR signal, Pulsar’s combination of sNETD (System NETD), fast thermal lenses, and refined image algorithms preserves thermal contrast and usable detection range.
This integrated approach keeps the image stable and interpretable even when weather conditions flatten the scene.
Explore Pulsar’s Axion Compact thermal monoculars
sNETD = Practical sensitivity in low contrast
Weather reduces temperature separation quickly, especially in fog, humidity, or thermal crossover. sNETD reflects how sensitive the full imaging system is under real conditions, not just the bare sensor.
A lower sNETD helps the device reveal small temperature differences when the scene is nearly flat, maintaining outlines, movement cues, and recognition confidence when ordinary NETD ratings would provide less useful detail.
Fog and drizzle absorb and diffuse part of the IR signal. Pulsar’s fast f/1.0-class objectives gather more infrared energy and deliver it efficiently to the microbolometer. This improves outline stability, keeps mid-range detection practical, and reduces the softening caused by moisture in the air.
High IR transmission of the lenses ensures more usable signal reaches the sensor as conditions worsen.
Moisture, snow, or heat can make animals blend into the background. Pulsar’s contrast and detail algorithms enhance thermal separation without adding artificial noise. These adjustments:
Processing cannot eliminate atmospheric limits, but it restores enough structure for confident spotting when raw IR input is weakened.
Whenever fog thickens, rain begins, snow intensifies, or heat settles across the landscape, small adjustments in how you operate your thermal can preserve contrast and prevent misidentification.
These habits counter the effects of atmospheric attenuation and help the sensor interpret limited infrared energy more accurately.
These simple actions maintain reliable detection and recognition even when weather rapidly reshapes the infrared scene.
Before changing positions or committing to a stalk, take a few seconds to evaluate how the environment is affecting infrared transmission. A short weather scan helps you adapt settings and expectations before you rely on the image.
This simple routine helps you decide whether to lower magnification, adjust sensitivity, recalibrate, or shift to terrain features that will give your device the strongest contrast.
Weather will always influence thermal imaging, but hunters who understand the physics behind fog, rain, snow, and heat gain a major advantage. Moisture absorbs and scatters infrared energy, and heat narrows temperature differences, yet none of these conditions make thermal optics ineffective. They simply require more deliberate scanning, more frequent calibration, and smarter use of terrain.
By recognizing how atmospheric changes affect thermal contrast and by relying on equipment built for adverse conditions, hunters can keep their detection and identification confidence high in any season.
Pulsar devices combine sensitive sensors, fast germanium optics, and intelligent image processing to preserve clarity when conditions shift, helping you stay aware and effective even when the environment works against visibility.
Ready to take the next step? Explore Pulsar’s field-proven thermal devices to find the system that performs with you, not against the weather.
Thermal can see into fog but not fully through it. Fog droplets absorb and scatter LWIR energy, which reduces detection range and softens outlines. Light fog is usually manageable, but dense fog causes contrast loss that limits identification.
Yes. Rain reduces thermal contrast because droplets absorb IR energy and wet surfaces cool rapidly. This creates thermal equalization between animals and the background, shortening recognition and identification range. Light rain has mild effects; heavy rain has strong effects.
In most cases, yes. Night vision depends on reflected light, which fog and rain scatter heavily. Thermal imaging detects emitted heat, which passes through moisture more effectively. However, severe fog or heavy rain still reduces contrast for any LWIR device.
Often, yes. A cold, uniform snow layer creates strong contrast that makes warm animals stand out sharply. But falling or blowing snow can scatter IR energy, and wet snow on fur can reduce emissivity. Snow helps detection but can occasionally hurt fine detail.
Heat causes background warming, narrowing the temperature gap between animals and their surroundings. As the scene reaches similar temperatures, contrast collapses, making the image look flat. This is most noticeable in midday heat or early evening after sun exposure.
Thermal crossover is a short window when ambient temperatures equal animal temperatures. It occurs twice per diurnal cycle: around sunrise and shortly after sunset. During crossover, detection range drops sharply and animals blend into the background.
Detection range decreases significantly when moisture absorbs or scatters LWIR energy. In heavy fog, rain, or humidity, long-range visibility collapses first. Mid-range detection usually remains possible, but recognition and identification require shorter distances and slower scanning.
Use higher sensitivity modes, lower magnification, and moderate contrast adjustments. Frequent calibration (NUC) helps stabilize the image. Black Hot often improves shape visibility in moisture, while White Hot helps track subtle movement.

Julia Nowak was born and raised in a hunting family in Poland and now lives — and continues to hunt — in Sweden. She holds a degree in sustainable forest and game management, bringing both tradition and scientific knowledge to her pursuits.
For Julia, hunting is not just a hobby; it’s a way of life. She also runs the YouTube channel Hunting O’Clock, where she shares her experiences and insights from the field.
Before purchasing any night or thermal vision device, please make sure you adhere to the local legislation and only use it when it is allowed. Our ambassadors come from various countries and travel a lot, which allows them to test different devices. We do not encourage or support the illegal use of our devices in any events. If you wish to learn more about export and sales restriction policy, please visit the following link: Export and Sales Restriction Policy.