It's obvious that weather affects fishing. Weather can affect different trout water types quite differently though. Here are a few of the key weather effects that may change your fishing success.
Warm sunny weather in the Winter, Spring, and Fall can trigger hatches on rivers and streams but hot bright sunny weather in the Summer can pretty much shut things down. In the cool months focus your river fishing on the warmest part of the day and in the hot times focus on mornings and especially evenings for good caddis action.
Lake fishing for trout is notoriously variable according to weather. Bright sun and calm water, especially in the Summer, can totally shut down the fishing. Look for overcast conditions or at least light breezes to stimulate fish feeding on lakes. Larger lakes seem to be more affected by weather while small ponds often show little to no change.
Pay attention to the Barometer also. Rising pressures usually stimulate feeding and falling pressure can shut down the fishing. Pressure changes affect lakes the most but can also change the fishing on large rivers. Small fast flowing creeks are the least affected by pressure changes.
Remember that most hatches occur at almost the same time each year according to length of days, temperature, and water levels but some can be delayed or hurried by unusual weather. Spring and early Summer hatches happen faster when it warms much sooner than usual and are delayed when it stays cool longer than usual. Fall hatches can happen sooner than normal if it cools down sooner than normal or can also be delayed if it stays warm.
Getting in tune with the weather can increase your chances of knowing what to expect even before you hit the water.