UMPQUA Stream Thermometer Do know that most trout won’t feed in water that is colder than 50 F? Or that in warm water they stick to the riffles because the heat drives oxygen out of still water. The Umpqua Stream Thermometer will tell you if the water is ready for a hatch, too cold for feeding, or just right. Durable aluminum case, pocket clip and lanyard hole for easy carrying. Registers 20 F to 120 F