Can't make this stuff up.

[Swattie87]

About 10 years ago I experimented with 3-4 different thermometers. One was infrared where you point it at the water surface and the rest were the typical fishing thermometer. None of them ever seemed to agree. Some varied by 4-5 degrees (those ones were made in China). Which one should I trust?

I have also experimented at a USGS thermometer location on Tionesta creek. I found my hand held (the one I believed was my most accurate) was 3-4 degrees off what USGS was posting as their stream temp. I sent them a message but I never heard back. I imagine USGS is more accurate than me but if their thermometer is in direct sunlight would it artificially trend upward?

To test the accuracy, simply test the thermometer versus a glass of ice water, full of ice, but with water in it. You should read 32-33F. Calibrate accordingly.

My Amazon special el cheopo reads 32.5 when doing this, FWIW. Figure that’s close enough.

 

[Prospector]

I hope you all also don't make the mistake of laying the thermometer on the stream bottom because that is also not the accurate reading of the water. The bottom, especially if rock and in the sunlight, is actually much warmer than the water.

When I’m fishing streams where I wade I always hang the thermometer off my waders. So no problem there. When I fish small wild trout streams I’m not wading so I usually lay the thermometer down and come back for it.

 

[Nymph-wristed]

I have lost 20 of them over the years, so look closely in SEPA and NEPA and you might find a free one. Good tip from jifigz about dangling not just dropping it on the bottom. Although if it's good on the bottom and you're checking for fish safety not behavior, you should be good. Just don't **** upstream of it either or your calculations might be off...

Btw, Lenny is a good dude who's worked in the various shop locations since he was a youth. Add John Parisi to the list of solid, knowledgeable guys over there at TCO, too, even if I catch him guiding dudes in some of my favorite spots!

 

[jifigz]

I have lost 20 of them over the years, so look closely in SEPA and NEPA and you might find a free one. Good tip from jifigz about dangling not just dropping it on the bottom. Although if it's good on the bottom and you're checking for fish safety not behavior, you should be good. Just don't **** upstream of it either or your calculations might be off...

Btw, Lenny is a good dude who's worked in the various shop locations since he was a youth. Add John Parisi to the list of solid, knowledgeable guys over there at TCO, too, even if I catch him guiding dudes in some of my favorite spots!

Dude, this year in June on kettle in Ole Bull the bottom of the stream bed was registering like 78 degrees and, if you put your hand on it, the rocks felt like heaters. That is what my thermometer read at least while laying it on the stream bottom. The water was coming in at like 66 degrees if I submerged it but held it mid-water column. Obviously, the rocks are slowly warming the water, but that is a huge difference.

 

[McSneek]

I don't use a thermometer to determine if it's safe to fish, or not. I use it to tell me how the fishing will be based on the stream temp. Too cold and the fishing usually sucks. I have yet to fish a mountain freestone stream that was above 62F, ever in my life.

So you drive all the way to the stream and lo and behold your thermometer tells you the water is cold. What then, you drive somewhere else? Wouldn’t you anticipate cold water based on time of year, volume and air temps? Taking the water temperature is right up there with pumping a fish’s stomach after you catch it to see what it’s been eating.

 

[wildtrout2]

When I fish small wild trout streams I’m not wading so I usually lay the thermometer down and come back for it.

Me too, IF I remember to pick it back up. I'll bet over the years I've replaced roughly 8 of them. A few years ago I started attaching a piece of fluorecent tape to it, so I might see it more readily upon returning to the spot where I left it. That's IF I realize quickly enough I indeed left it behind.

 

[wildtrout2]

So you drive all the way to the stream and lo and behold your thermometer tells you the water is cold. What then, you drive somewhere else? Wouldn’t you anticipate cold water based on time of year, volume and air temps?

If it's too cold, the answer is yes to going elsewhere. You can "anticipate" stream conditions all you want, the only way to know for sure is to go to that particular stream to find out.

Air temps have little to do with stream temps in the mountains, where many streams get very little sunlight. I've seen where there was a full week of 90F+ temps, and the stream temp was only 56F. That's an example of what I mean. Also, streams within only a few miles of each other can have very different temps.

 

[6xAdams(Jones)]

Taking the water temperature is right up there with pumping a fish’s stomach after you catch it to see what it’s been eating.

That may be extreme... Unless you're taking the fish's internal temperature. (I think fish pumps are ridiculous and would probably push anyone using one into the creek.)

 

[Silent Ocelot]

Taking the water temperature is right up there with pumping a fish’s stomach after you catch it to see what it’s been eating.

I disagree about the use of a thermometer. I think it's a nice bit of tangible data to gather during fishing that can help refine an angler's decisions. I will say I am pretty good about guestimating the temp by being in it, others may say that it's not possible to get a good judge of water temps just by being in it.

I think stomach pumping is pretty stupid and inhumane. You're taking food out of fish so therefore there is a negative impact on that fish. Plus if you already caught a fish on a particular fly wouldn't that be indicative enough of what the fish are eating?

 

[Silent Ocelot]

would probably push anyone using one into the creek.)

or start tossing rocks.

 

[wildtrout2]

I disagree about the use of a thermometer. I think it's a nice bit of tangible data to gather during fishing that can help refine an angler's decisions. I will say I am pretty good about guestimating the temp by being in it, others may say that it's not possible to get a good judge of water temps just by being in it.

What I started doing a number of years ago, was to stick my hand in the water and guess what I think the temp is. Then I put my thermometer in for a few mins to get a reading. Now, my guesses are either spot on, or within a degree or two of the actual water temp. A few degrees in water temp can make all the difference in the world regarding trout activity.

 

[6xAdams(Jones)]

Keeping with the spirit of the thread, I'll say that one reason I do not carry a thermometer, is that I already have enough busyness attached to, or in the pockets of my 20+ year-old vest. Also, I'm very cheap. I'll buy a thermometer after I replace the rusty nail clippers that are tied to a D-ring with old monofilament.

 

[Prospector]

Me too, IF I remember to pick it back up. I'll bet over the years I've replaced roughly 8 of them. A few years ago I started attaching a piece of fluorecent tape to it, so I might see it more readily upon returning to the spot where I left it. That's IF I realize quickly enough I indeed left it behind.

Same here. I put a long lime green cord on the one I lay in the water. When fishing wild streams I have a small pack that holds only 1 flybox. I leave my big vest with the 9 fly boxes, and other unnecessary stuff I carry, at home. The big vest does help me keep my trapezius muscles in tip top shape.

 

[Prospector]

So you drive all the way to the stream and lo and behold your thermometer tells you the water is cold. What then, you drive somewhere else? Wouldn’t you anticipate cold water based on time of year, volume and air temps? Taking the water temperature is right up there with pumping a fish’s stomach after you catch it to see what it’s been eating.

It’s just more information at your disposal.

Where it comes in handy for me is when the temps are trending up. I want to hit a stream that typically is on the colder side so having prior knowledge I don’t waste time driving to a warmer one. The most stream temps I’ve captured on one day is 7. One was a mid June day. The coldest one ended being my target for that day but I checked 6 others along the way. They varied between 52 and 60 degrees.

One year on July 4th I took 7 readings (different group of streams) I found a range of 57 to 72. Only 3 were fishable that day.

That seems like useful info for later in the summer as things warm up and knowing where it might be safe to fish. Some days I’m very surprised. I’m glad I’ve taken the time to build an inventory of sorts but there is always a stream cold enough to fish near my camp. Some are no brainers others are not.

 

[krayfish2]

I still have a cheapo plastic 🌡️ I got at Clousers in the mid 90's. Thought I lost it so I got some metal cased one that's tied to 5' of 50# braid. Hang it off the boat or clip it to my belt loop. Ended up finding the first one after I dropped the $20 for the new one. Rarely use it since I usually know if it is going to be fishable temps before I even load the car.

Skip the stomach pump. Just fish for smallies. Don't need pumped, they'll just puke crayfish all over your hands as you remove the hook.

 

[wgmiller]

I attached a boating key float to my thermometer. Haven’t had a problem losing one yet!