From the standpoint of evolution, dogs have survived extreme weather quite well over thousands of years. The last 200 years however have brought a change in breeding selection. Man has replaced mother nature in the breeding selection process. We have increasingly been selectively breeding retrievers to build their drive, and one of the effects has been the elimination of the "off switch" in many retrievers. Today many retrievers will keep going even though it may kill them. It is the responsibility of today's retriever owner to learn how to act as a governor on some of the dogs activities, in order to keep him safe.
Every dove season in the south there are a number of dogs that die from heat stroke. Those deaths are easy to prevent. Hunter's traditionally get wrapped up in learning and recognizing the symptoms of heat exhaustion and trying to manage the problem after the symptoms appear. That is a high risk strategy. The smart way to deal with heat is to help the dog manage his heat levels on the front end. Manage the heat and keeping the symptoms from appearing is the safest strategy for your dog. Basically it boils down to moderating his acitivity level and keeping him wet or damp on the outside when he is working in high temperature conditions.
The most dangerous general activity for your retriever is working in high temperature, high humidity conditions. A dog's normal body temperature is 101 degrees Fahrenheit to 102.5 degrees Fahrenheit . Strenuous exercise will spike that body temperature up to the range of 106 degrees to 108 degrees. The dog's body cannot withstand that high a temperature for extended periods. He will go into irreversible heat stroke and die. He has to lose some of that body heat fairly quickly. A major tool for the handler to cool him is to moderate his activity. If it is 95 degrees and you have 3 doves downed in a soybean field and the dog has just hunted vigorously for five minutes before returning with the first one, don't immediately send him for number 2. Sit him down in the shade for 10 or 15 minutes and let him lose some heat. Then send him for the next downed bird. Moderating his activity levels will keep his body heat at manageable levels.
Your second major tool for helping your dog fight heat is evaporation. Evaporation literally sucks heat out of the air in the vicinity of a wet surface. That is why you feel cool when you walk into a forest. As part of their metabolic cycle trees evaporate water off of their leaves. A single tree evaporates hundreds of gallons of water per day. A building benefitting from the active evaporation of trees will experience a 17% reduction in cooling requirement. Just think of the benefit of a 17% reduction in heat to a dog on a hot day.
When water evaporates and goes from the liquid to the gaseous state is literally absorbs energy in the form of heat. When you step out of the shower and feel chilled, that is evaporation working. Evaporation can lower the temperature in the immediate surrounding area five to ten degrees. Evaporation is also proportionate to the surface area that is wet. With a dry dog, evaporation is limited mainly to the surface area of the mucous membranes of his nose, mouth, and throat. With a dog that wet over his entire body, evaporation is increased hugely, and the dog can much more readily lose heat.
When you are hunting in hot weather, a good practice is to start with the dog wet and keep him damp if possible. That way you start with him cool and help him to stay cool from evaporation.
Several cautions are in order for wet dogs and heat.
1. Don't put a wet dog in an enclosed space like a dog crate. The lack of air circulation will severely curtail evaporation and allow heat to build up.
2. Before counting on a small pond to cool your dog, stick your finger in the water. If it feels warm, then immersion is not going to cool the dog. Put him in for a moment to wet him down, then bring him out for evaporative cooling to go to work.
Manage your dog's heat levels long before he gets too hot. That is the best protection against heat stroke.
Cold water can kill your dog also. Cold water acts as a heat sink and sucks the body heat off of the dog. The length of time the dog is in the water is the critical factor. The longer the immersion, the more heat the dog loses. A major management tool is again moderating his activity. If you have knocked down 3 ducks and the dog just spent 5 minutes swimming in cold water to collect the first one, get him out of the water and let him build back body heat for 10 or 15 minutes before sending him for the next one.
Keep him out of the water when he is not retrieving. If pup is standing in shallow water, it still robs him of body head, just at a lower rate. Put him on a stand, a log, in the boat; some place where he is completely removed from the water. Get him a neoprene vest. The vest will greatly help him retain body heat. Also try to place him where the wind is blocked. Wind removes body heat also.
Don't give your dog a bath during waterfowl season. Soap and detergent wash the oils out of his coat and rob him of his natural water proofing. That robs him of a lot of body heat when his insulating undercoat gets wet.
Lastly and most importantly, watch out for ice. One of the most dangerous situations for the dog arises when he is hunting on ice and breaks through it. He may not be able to climb out. If you have ever watched or helped a dog climb into a boat, you have seen that he needs to get purchase on some surface with his back feet to propel himself up into the boat. We usually offer a substitute in the form of a hand on the back of his neck which allows his front legs to gain the additional leverage necessary to pull himself up into the boat. When he falls through thin ice he may not have the hind leg purchase to pull himself back up on the ice. If you can't get to him to give him a hand, then he will probably die of hypothermia. Be very careful when hunting a dog on ice. Make sure you have a back-up plan in the event he breaks through. A boat is the major tool for an ice rescue. You can use the boat to break the ice out to the dog, or with thicker ice, slide the boat out on the ice to get to the dog. A backup plan is a necessity for hunting on ice with a retriever.
A little attention spent on heat management in extreme temperature settings either hot or cold, will go long way in helping your dog deal with a hostile environment.