There are few beginning fishermen who haven't asked themselves when the ideal times and conditions are for fishing. Many people who have been fishing for some time ask themselves the same thing. Have you ever noticed though, that some people go out and seem to have great fishing luck, every time?
They do have a secret. It is this: In the real world, there are rarely "ideal" conditions and times for fishing. Instead, they key on the "most" ideal times and conditions, which is something entirely different because of the word "most". That is taken to mean, if these conditions exist, your chances of success are better when trying to catch fish.
Even the question of what the most ideal times and conditions for fishing can be difficult to answer, though, because of a few important factors. What are you fishing for? Are you fishing in a lake, stream, river, or the ocean? Are you fly fishing, lure fishing, or bait fishing? It sounds complex, but it really isn't. Each type of fish, body of water, and type of fishing simply combine to dictate the most ideal times and conditions for catching fish.
This can be broken down a little, and it is often easiest to talk about when the least ideal times and conditions are.
For instance, fishing for trout or salmon in a river, stream or lake may not be the best if it is during or right after a full moon. In the summertime, the full moon at night brings out the insects, so the fish can feed extensively. Fish that are full from a night of feeding aren't nearly as receptive to taking the fisherman's offering, regardless of the type of fishing you do, as fish that are hungry.
For trout, salmon, and other cold-water fish, the best times of day are still shortly after dawn, and shortly before darkness. During times of the full moon at night, though, just before dark will probably result in a larger catch, since the fish haven't fed a great deal during the day.
On the other hand, if you are fishing for catfish, and provided it is legal in your area to fish after dark, nighttime is one of the most productive fish times. Even with catfish, though, nights with a full moon tend not to be quite as productive since the more moonlight they have, the more insects attracted to the water and the harder it is to get the fish interested in your bait rather than in something else in the water.
The temperature of the water plays a large part, too. Even warm water species like bass, perch, bluegill and catfish, become sluggish if the water gets too warm. They tolerate the warm water better than cold-water fish like trout, but they usually won't be very receptive to taking a fly, lure, or bait if the water temperature is too high. This means that the middle of the day, on a hot day, normally isn't going to be very productive. Water takes some time to heat up, but it takes just as long to cool down. What few fish are caught under the blazing sun will often be on the bottom, in vegetation, in hollows, or under logs; each of which tend to be a little cooler than surrounding areas.
For many of the reasons mentioned above, just before, during, and after a rainstorm can be tremendously productive for any of the fish already mentioned, as long as the storm isn't prolonged. The rain clouds shade the water and the rain drops the air temperature, which allows the water to begin to cool. What's more, the rain is likely to knock insects into the water, initiating a behavior in the fish that is very much like a feeding frenzy. In a prolonged storm, though, the fish may become full and stop showing interest in striking flies, lures, or bait.
In lakes, especially the crystal clear ones, a slight breeze is also a good condition for all three kinds of fishing. The ripples in the water act like tiny prisms, breaking up your outline, making it more difficult for the fish to see you. This can be especially useful to a fly fisherman, however, since it masks the minute disturbances caused by the fly line landing on the water.
In rivers and streams, one condition that is rarely thought about is the one dealing with water flow. It is true that the early steelhead and salmon runs often coincide with increased flow due to snow melt off in the high country. However, if the flow is greatly increased, the water is also carrying a larger amount of sediment and debris. So while the fish are present, they may not be easy to catch.
Still, if the flow drops too low, the water isn't moving as quickly and it can warm up faster. This is also not good for fishing.
The best flow is steady, with enough water to maintain cool temperatures. For most rivers and streams, the ideal flow happens every year for a period lasting between a few days and a few weeks.
There are other variables that haven't been discussed here, but just from the above, it is pretty easy to see that regardless of body of water, type of fishing, or kind of fish being sought, ideal conditions and times are rare, especially in combination. Many of them can't be planned for, either. We can know well in advance when there is going to be a full moon, but we have no way to know for sure when it will rain, when there will be a slight breeze, or when melt offs will increase water flow.
In over 45 years of fishing, in many bodies of water and for various kinds of fish, and often fishing many times a week, I've encountered truly ideal conditions three times. In each instance, it didn't last long, but it didn't need to because I caught my limit or the maximum number I could use, each time and within less than an hour or two. I won't say I haven't had tremendous success during other times, and there have been a few, during times and conditions that weren't the best for fishing.
Knowing the ideal conditions and times to fish is helpful, but they aren't the most important consideration for fishing success. Still, knowing when conditions and times are poor for fishing can at least allow the fisherman to have realistic expectations. If they then exceed those expectations, they have had a great fishing day.