Late fall and winter is the time of year when there can be big swings in air temperature from week to week. While these variations in temperature are easy to detect, other substantial changes may be overlooked. As an example, a couple weeks ago I took an early morning drive to Wyoming’s Green River to fish. During the three hour drive my truck’s outdoor thermometer reminded me how rapidly temperatures can change over short distances. The predawn temperatures I saw ranged from 16 to 34 degrees. The coldest air was at the bottom of the valleys while the warmest temperatures occurred in the mountains.
It is these differences in air temperatures that cause predictable canyon winds. After the sun sets, air cools fastest along the canyon walls. This air is denser so it starts to sink. As it moves downhill, it becomes wind. When this moving air reaches the mouth of Logan Canyon, it gains speed as it exits this narrow gap. The wind then reverses direction as the sun warms the mountains and the expanding air mass rises. This simple process is one all big game hunters can use to their advantage. It should affect the direction one walks and alter the location someone sits to look for game depending on whether it is morning or afternoon.
Changes in temperatures play a role in many of the broadscale patterns hunters and anglers need to understand. Dropping air temperatures that correspond to shorter day lengths are what induce ducks to migrate and trout to spawn. Rapid changes in air temperatures affect animal movement. Deer will generally move more when temperatures drop by 10 degrees from one day to the next.
Given Utah’s short rifle season, big temperature drops during the season can greatly improve hunter’s success. The same thing can happen with waterfowl. If temperatures drop enough to freeze shallow sloughs, ducks will need to seek out other habitats. If you know where those other habitats are, you can increase the number of ducks harvested.
Upland gamebird hunting with dogs is another activity where it helps to pay attention to air temperatures. There is evidence of a Goldilocks relationship between air temperature and upland bird hunting success. Cool moist air holds more scent for dogs to detect. Cooler temperatures also allow dogs to cover more ground without overheating. The combination of these factors means more birds will be flushed when air temperatures range between 35 and 60 degrees. As temperatures drop below freezing, the moisture and scent freezes out of the air so dogs have a more difficult time detecting birds.
When temperatures are too high, there is less scent to detect and the dogs tire faster.
Air temperatures affects other aspects of hunting such as how long you have to butcher an animal. When temperatures approach and exceed 60 degrees, meat will spoil quickly. The daytime temperatures we have now (32- 45o F) allows you to let your birds and big game hang for a while in an unheated garage to foster enzymatic breakdown. Any animal harvested this time of year should be gutted but final processing can wait a day or two.
In almost all fishing situations, water temperature is one of the primary predictors of success. But much like on land, water temperatures are not the same everywhere. Fish in lakes and reservoirs will move into shallows in search of warmer water. South facing slopes with a dark lake bed will warm faster than north facing slopes with a more reflective substrate. During summer, lakes that are deep enough have a zone of warm water sitting on top of colder water. Lake systems that stratify in this manner can produce both cold and warm water fish species.
The best way to improve your understanding of how temperatures affect hunting and fishing is to have a journal to record your efforts and success. In this journal, note environmental conditions such as temperature, cloud cover, precipitation and winds associated with each outing. For hunting, air temperature will be sufficient. For a fishing journal, record both air and water temperature. Keeping a journal will improve your understanding of how temperature affects success. You can then use this knowledge to plan hunting and fishing trips to places, at times, and in conditions when your chances of success are high.