Remember trout are cold blooded and they're the same temperature as the water they swim in.

     For spring trout fishing its best if the air temperature is above 40 degrees and rising.  Then the stream temperature will follow and the trout should hit.

     The immediate effect of water temperature going down in the spring is trout quit feeding.

     After the spring flood, when the stream returns to normal flow, the angler can find the best fishing for big trout. 

SPRING CREEK TREASURE, Wisconsin's 100 Best Trout Streams  Page 12

     For spring trout fishing it is best if the air temperature is above 40 degrees and rising....However, there is an exception.  When snow is on the ground, and the air temperature rises above forty-five degrees, the snow will increase melting to the point where cold water will be flowing into the stream, which causes the water temperature to go down.  The immediate effect of water temperature goind down in the spring is trout quit feeding.