Not to worry, the water surface temperature gauge built into almost all fish finders these days can lead you to them.
Fish are cold-blooded, not like the CEOs currently under indictment. I mean to say their body temperature is the same as the temperature of the water around them.
Lower water temperatures mean a slower metabolism for fish causing them to be less active, and they don't need to feed as often. Higher temperatures speed up their metabolism requiring them to feed more often to fuel their increased activity.
A degree in rocket science is not required to figure out that fishing warmer water is going to be more productive than fishing colder water, and all we need to do is find it.
The sun stays closer to the southern horizon as it travels daily from east to west during winter and spring, which means you are more likely to finder warmer water on the north side of a lake, cove or saltwater bay. Objects like rocks, stumps and fallen trees that reach from the bank into the water tend to soak up sunlight and transmit their warmth to the water.
Look for rocky points and shorelines, stretches of riprap, stump beds and blow-downs along northern shores. Your temp gauge will help you pinpoint the warmest water in these areas, and that is where the hungriest fish are most likely to be found.
Dirty water is generally warmer than clear water because the sun warms the suspended "dirt" particles, and they pass the heat to the water around them. Dirty water can be found where rivers, creeks and washes drain into a lake or bay after a spring rain. Spring storm fronts can move through every couple of days, and their runoff is usually warmed as it trickles over the ground into these arteries, and it often carries food that attracts fish and baitfish.
During periods of clear, windy weather, dirty water can often be found on windward shores. Warmer surface water is blown against that shore, and wave action against the bank stirs up the bottom.
Saltwater anglers fishing open water sometimes encounter a temperature shear along the boundary between two conflicting currents. If there is a water clarity change with the temperature difference, it makes the shear line easy to see. If not, you may only be able to detect it with your temp gauge. Fishing can be better on one side of the shear or the other depending on the time of year and the species of fish being pursued.
Common surface temp gauges are not typically accurate enough for scientific research, but they deliver readings consistent enough to help you find the warmest water and avoid the coldest.
It is important to move your boat slowly as you search because the sensors generally don't react quickly enough to show temperature changes in real time. A layer of marine growth or road grime on the contact surface of a temp sensor can slow its ability to sense changes, so they should be kept clean, too.
Finally, if your transducer is glued down in the bilge area to shoot through the hull, its temp sensor can't touch the water. Most of today's sonar transducer manufacturers fix this problem by offering "Y" cables that let you mount a separate temp sensor on the outside of your transom hull.