Rain Temps vs. Lake Temps

[JBMasterAngler]

So it's going to be sunny and warm this week, then it'll drop about 15 to 20 degrees and rain. I'm assuming the rain will still be a little warmer than the lake water? Let's say we get 1 inch of rain in the east metro this weekend, how much could that affect the lake temps? I know it depends on the lake also, but let's keep it basic.

[pushbutton]

jb, you either have too much time on your hands or really got the "bug" bad to be thinking about this stuff at 5:15 in the morning since i was a c student in algebra my temperature formulations are not going to be much help to you, but would have to say the rain would help raise the lake temps slightly, ever so slightly. if your going to be in cold spring area on sat. night let me know, i could probably hook you up with a few cats around dusk.

[OnAFly]

You caught my interest with that question and I dove into my thermodynamics book to find the answer (I was bored at work)...then I remembered why and how much I hated thermodynamics...and still do.

[BobT]

Does an inch of water on a lake containing millions of gallons really have even a measureable effect? I think of it this way. If you add a drop of boiling water to a cup of ice water would you be able to measure the temperature rise?

[OnAFly]

Ok, this was bugging me.

Using the definition of Specific Heat

Q=pVc*Delta T

Qlake+Qrain=Qfinal

(VrTr+VlTl)/((Vr+Tr)=Tf (since specific heat and density are constant)

For a 400 acre lake of average depth of 20 ft at a temp of 40 degrees F with an inch of rain at 55 degrees F:

Tf = 40.0615F

So neglecting any runoff, and only the mixing of the rain with the lake, the increase is very small since the temperature difference is small.

[pushbutton]

see jb, you found someone else with too much time on their hands ...very nice response OAF!!!

[Nick Kuhn]

Water temps will warm slowly but steadily until a thermocline starts to form, at which point water temps will follow air temps fairly closely.

[FutbolGuru]

However, if you're fishing the windward side of a lake while its raining or as soon as it's done receiving warming rain... You'll find the spot you're fishing to be a little warmer than the rest of the lake...

[JBMasterAngler]

I figured run off would be an automatic inclusion, and would actually warms things up more than the actual rain itself dropping onto the lake surface. Basically to sum it up, it's not going to make a significant change? I guess my main goal was to find out if while raining it'll bring in the fish to shallower water. But I guess that would have more to do with food washing into the lake than the temps going up.

I wish I could say 5:15 is the time I wake up and go fishing, but that just wouldn't be the truth. It's my "unwind" time after work

[mn_bowhunter]

Rain is formed higher up, which has colder temperatures. The rain will be cold too so I wouldn't expect a change.

[OnAFly]

If the weather can get stable and the wind would die down the fish would move up, but at it is right now, they're sitting in or near the same places they were 3 weeks ago.