Quick guess at water temp

[GoneFishingLTN]

Is there a way/guide to guess the avg water temp if you don’t go out to a lake on a boat? Like if the air temp been 45 high then 20s at night etc

[WRB]

If you can walk on it it's frozen.

Really depends on the weather over a longer period of time, what was the average temps the past 2 weeks? The water will not be higher then averaged day + nights temps.

Tom

[Deleted account]

12 minutes ago, GoneFishingLTN said:

Is there a way/guide to guess the avg water temp if you don’t go out to a lake on a boat? Like if the air temp been 45 high then 20s at night etc

No. I usually bring a thermometer or stick my finger in it. You can get pretty good from feeling slow rolled spinnerbaits right after you bring them in, or the fish themselves.

[Gundog]

The rule I go by is you take the high temps for the last 6 days and the low temps for the last 6 days. Add the high temps up and divide by 6. That will give you an average high temp. Do the same with the low temps to get an average low temp. Add both numbers together and divide by 2 to give you an approximate water temp give or take 5 degrees. This doesn't take into account snow melt which will decrease the water temp. This is just a method I use when no water temp gauge is available. 

[senile1]

If you have a source of fishing reports for your lake, that will give you a surface temperature that is fairly accurate.  The size of the body of water makes a huge difference.  Where I live I can have 5 or 6 days of warmer weather in January and the temperature at one of the lakes, 7190 acres, would still be below 40 if the starting temperature was 33 or 34.  Smaller lakes of 50 - 200 acres would warm up quicker.  Personally, I wouldn't venture to guess based on any averages of day and night temps unless the lake were quite small.  Then, maybe you could work something out.

[scbassin]

When my mom use to take us kids swimming she would walk down to the waters edge & stick her big toe in it & determine if was warm, hot or cold before we could go in. Or you could buy an Aquarium thermometer & use it.  

[senile1]

1 minute ago, scbassin said:

When my mom use to take us kids swimming she would walk down to the waters edge & stick her big toe in it & determine if was warm, hot or cold before we could go in. Or you could buy an Aquarium thermometer & use it.  

Nothing is more accurate than the toe method.  

[Team9nine]

No way to know for sure...too many variables at play. Drop $5 or $10 bucks for a pocket thermometer and never wonder again.

 

[Deleted account]

1 hour ago, Gundog said:

The rule I go by is you take the high temps for the last 6 days and the low temps for the last 6 days. Add the high temps up and divide by 6. That will give you an average high temp. Do the same with the low temps to get an average low temp. Add both numbers together and divide by 2 to give you an approximate water temp give or take 5 degrees. This doesn't take into account snow melt which will decrease the water temp. This is just a method I use when no water temp gauge is available. 

Yes, but that doesn't take the curvature of the earth into account...

 

[Fish the Mitt]

2 hours ago, WRB said:

If you can walk on it it's frozen.

I know this one guy... 

 

 

 

 

 

As for your question:

Yeah, there are too many variables to figure it out based on air temp. Surface area, depth, current generation, inflow/exflow, precipitation, etc..

 

Even with the whole add this and this together and divide by this and multiply by this, won't be consistent - much less accurate.

 

This is a heat transfer and hydrology question. If anyone had an answer, it would have been @Team9nine and he says get a pocket thermo. So... get a pocket thermo.

[WRB]

If you use a thermometer your not guessing!

Tom

[Paul Roberts]

Yes. Although, you should ground truth it on your waters to get a more accurate bead on heating. Nature can be capricious.

 

In general, if you look at the average daily temperature over a couple days time the shallower waters (~<8fow) will follow with a delay of a few hours time. The deeper you go the more buffering there is. Bright sun with calm conditions heat best. Overcast and calm still heats, but less. Wind will roll up cold water however.

 

I've taken temperature profiles for years so I have a good idea of how water bodies heat. At one time I fished and took temps so much I was accurate to a degree F by touch alone. Wish I could still fish that much.

[Scarborough817]

3 hours ago, Team9nine said:

No way to know for sure...too many variables at play. Drop $5 or $10 bucks for a pocket thermometer and never wonder again.

 

was this this taken today?

[Cak920]

There are a huge amount of variables that go into the water temp. For 5 dollars on eBay you can by a aquarium thermometer with a probe to check the temp.

[lo n slo]

fwiw, try calling your local water treatment facility (drinking water, not waste water). they constantly monitor raw (lake) water conditions, including temperature. as a general rule, temps on smaller bodies of water will fluctuate quicker than larger ones but should be within 5 degrees, or so, of each other.

[WRB]

With a pocket thermometer you need to wade in waist deep to read it.

Tom

[Team9nine]

55 minutes ago, Scarborough817 said:

was this this taken today?

 

Nope, Dec 10, 2017 as our waters were bouncing between iced up and not. Local reservoir Sunday was only 43 though, so we haven't gained much. 

 

You can try and guess all you want, but if you don't have an accurate starting point as your basis, or a calibrated finger like @Paul Roberts , you're totally guessing, and the worst part is you'll have no idea how right or wrong you are. A small shallow pond where the correlation of heat transfer is more direct, you might get close, but a larger body of water like a reservoir where you could easily have 10 degrees difference or more within creek arms or between headwaters and lower end - good luck...and be sure to wear your waders if you walk in waist deep to take readings ?

[Scarborough817]

15 hours ago, Team9nine said:

 

Nope, Dec 10, 2017 as our waters were bouncing between iced up and not. Local reservoir Sunday was only 43 though, so we haven't gained much. 

 

You can try and guess all you want, but if you don't have an accurate starting point as your basis, or a calibrated finger like @Paul Roberts , you're totally guessing, and the worst part is you'll have no idea how right or wrong you are. A small shallow pond where the correlation of heat transfer is more direct, you might get close, but a larger body of water like a reservoir where you could easily have 10 degrees difference or more within creek arms or between headwaters and lower end - good luck...and be sure to wear your waders if you walk in waist deep to take readings ?

well considering the ice that is forming in my guides i would assume its around 33

[J Francho]

2 hours ago, Scarborough817 said:

well considering the ice that is forming in my guides i would assume its around 33

Water temp could be 80°, and air temps below freezing, and you'll get ice in the guides.  I know that's extreme, but you get the point.  I'll fish winter streams that might 40° water temps, but air temps half that, and guides freeze up. 

 

I've use a pool thermometer, and cast it out, let it sit, and read the temp.

[Scarborough817]

1 hour ago, J Francho said:

Water temp could be 80°, and air temps below freezing, and you'll get ice in the guides.  I know that's extreme, but you get the point.  I'll fish winter streams that might 40° water temps, but air temps half that, and guides freeze up. 

 

I've use a pool thermometer, and cast it out, let it sit, and read the temp.

just have to use my ibobber for temp 

[MassYak85]

On 3/21/2018 at 10:31 AM, Gundog said:

The rule I go by is you take the high temps for the last 6 days and the low temps for the last 6 days. Add the high temps up and divide by 6. That will give you an average high temp. Do the same with the low temps to get an average low temp. Add both numbers together and divide by 2 to give you an approximate water temp give or take 5 degrees. This doesn't take into account snow melt which will decrease the water temp. This is just a method I use when no water temp gauge is available. 

I think this is about as good as you can get for a guess. The two things I'd also consider are major flows (river, rain) into the lake/pond like Gundog said, and also the size of the lake. Huge reservoirs may take weeks or months to get anywhere near the rising air temperatures. 

[flyfisher]

On 3/21/2018 at 12:19 PM, reason said:

Yes, but that doesn't take the curvature of the earth into account...

 

because the earth is flat....duh

[TnRiver46]

Usgs website has water temp for several sites, I look at it daily 

[Paul Roberts]

On 3/21/2018 at 3:33 PM, Team9nine said:

 

Nope, Dec 10, 2017 as our waters were bouncing between iced up and not. Local reservoir Sunday was only 43 though, so we haven't gained much. 

 

You can try and guess all you want, but if you don't have an accurate starting point as your basis, or a calibrated finger like @Paul Roberts , you're totally guessing, and the worst part is you'll have no idea how right or wrong you are. A small shallow pond where the correlation of heat transfer is more direct, you might get close, but a larger body of water like a reservoir where you could easily have 10 degrees difference or more within creek arms or between headwaters and lower end - good luck...and be sure to wear your waders if you walk in waist deep to take readings ?

Yes, small and shallow waters are MUCH easier to get a bead on. The way heat gets distributed makes deep waters -that can hold onto masses of heat- both more stable to outside heating, but potentially more volatile when winds kick up. Then there are tributaries...

On 3/22/2018 at 7:08 AM, Scarborough817 said:

well considering the ice that is forming in my guides i would assume its around 33

Jon's on that one... He and I have both spent some time winter steelheading. They say the Inuit use something like 80 different words to describe ice and snow. Don't know if that's true, but I can certainly imagine it.

 

Quite a while back now, I wrote an article about winter trout fly-fishing. In it I stated that air temps below ~27F created such hard ice in the guides and on the line that fishing -with fly-line- became impractical. The heavy-handed Editor changed that number to 32, among other things.

[Joshua Vandamm]

On 3/23/2018 at 11:38 AM, Paul Roberts said:

Yes, small and shallow waters are MUCH easier to get a bead on. The way heat gets distributed makes deep waters -that can hold onto masses of heat- both more stable to outside heating, but potentially more volatile when winds kick up. Then there are tributaries...

Jon's on that one... He and I have both spent some time winter steelheading. They say the Inuit use something like 80 different words to describe ice and snow. Don't know if that's true, but I can certainly imagine it.

 

Quite a while back now, I wrote an article about winter trout fly-fishing. In it I stated that air temps below ~27F created such hard ice in the guides and on the line that fishing -with fly-line- became impractical. The heavy-handed Editor changed that number to 32, among other things.

@Paul Roberts one place I fish is a very deep quarry. Do you know if is there a decent equation or graph for determining stratification, temp at a given depth? Eg. Given: surface temp, rate of change, shallow subsurface temp( 4-10ft), x Coeficient, #ft (target depth)

 

With or without factoring in current, clarity etc?

 

Thx!