For centuries major battles between armies were fought during daylight hours because darkness meant blindness. Of course small bands of soldiers have always operated at night, gathering Intel, harassing the enemy, and committing acts of sabotage since conflicts began thousands of years ago, but battles for the most part were fought when opposing forces could see each other.
Flaming torches would have been carried in years past to light up pathways and trails, but the torches were a beacon that allowed others to track the progress of their rivals.
To operate at night without artificial lighting meant you needed to know the terrain well, and in most cases armies on the move did not always get to choose the location of battle, and even if they could they did not have the time to map out the area.
Today however, technology allows for unrestricted night operations. Terrain can be lit up without giving away the location of those conducting the operations in the dark. Soldiers, law enforcement and others can now see at night, because of technology.
This means that targets can be engaged at night as well. There are of course limitations and usually Mother Nature has a hand in the limitations. Rain, snow, cloud cover, sand storms, and other acts of nature play a role in the effectiveness of the technology.
Okay So What Has All of This Have to Do With You
The grid goes down and Martial Law or even nighttime curfews are enacted, but its dark and no one can see you right. Well, you can be seen if someone is looking with the right equipment. Drones and manned aircraft can detect heat signatures inside of structures from hundreds of feet in the air. If you are huddled up inside a structure, you may only think you are hidden in the dark. The right technology can determine what room you are in and on what floor.
If you slip outside to do some Intel gathering you can be tracked, and all of your movements recorded. The darkness is no longer cover if technology is used against you.
Things You Can Do
There are no absolutes when it comes employing counter measures against thermal cameras. It is difficult, if not impossible to defeat the technology with what you would have available. There are some that claim there are cloaking devices available or will soon be available. There may be such devices, but do you have one, can you get one, and more importantly how confident are you that it would work if you did have one?
You Can Make Detection More Difficult By Confusing the Operator
You are not trying to confuse the cameras, but instead are trying to confuse the humans analyzing the data. Cloaking devices if they do work would likely leave a black hole against the background however. Whatever cloaks you will cloak the background, as well, and this stands out. To a trained operator this indicates that something is there. They may not be able to tell if it is human or not, but only humans would or could cloak themselves or equipment, so there you have it. A red flag like a black hole may warrant closer inspection. Someone may be sent in to get eyes on the object.
If you have a basement and are worried about drones or other aircraft scanning to see the number of occupants in the home you may be able avoid detection by gathering in the basement as long as the basement is below ground level. However, heat signatures will be all over the home, from electrical devices, to lanterns to candles you may have lighted and then extinguished. If you sat in a chair the chair may still emit enough body heat to show up on a thermal camera.
You can use thermal blankets to contain your heat signature or the signature from appliances, or furniture. The blankets are not foolproof, but they could reflect the heat to the point where it may look like a small rodent, cat, or dog instead of a human or a heat signature that would indicate a human presence. Heat will essentially leak through, but not necessarily enough to determine what the object may be.
If outside you can blend in with warm objects such as steam vents if in an urban area or get close to brick/stone walls that would have absorbed heat during the day. Getting next to generators that are not your own could work as well.
However, keep in mind in certain situations there may be people looking for energy sources such as generators and steam vents, and they would use thermal cameras to find the heat signatures.
Heavy foliage, rain, fog, and snow can reduce your heat signature, so do nighttime maneuvers, if you can in the rain, snow, or fog. When traveling at night stay in the brush, walk along or even in rivers, streams or along bodies of water to help confuse the analysts.
Carry thermal blankets with you, and if at home or in any structure a wool blanket can even help somewhat, but again it is not a guarantee, but anything you can do, you should do, to break up your image and reduce the heat that the cameras see.
Glass is also known to reduce/block thermal imagining. How practical this might be depends on the situation and possibly the glass itself. Nevertheless, the more you know the better off you will be. A typical office building usually has numerous glass windows.
If the grid is down some people will experience darkness like never before, because many are not aware of how much light is available in the world from artificial light that bleeds over. The street light down the block, a neighbors’ porch light and the combined lighting from cities large and small all fight back against the darkness. When cities go dark you are essentially blind at night except for the artificial lighting you may carry, but it may only allow you to see a few feet or a few yards in any direction. You are blind in the darkness but others may not be.
Cameras pick up heat and the data is arranged so the operator can see an image, and then possibly determine what that image is. Human shapes are readily identifiable, so you have to do what you can to make it harder for the analyst.