Water Temperature by Species: The Cheat Sheet

Why temperature comes first

The USGS describes water temperature as a major influence on biological activity and growth: every fish species has a preferred range, and its numbers fall as the water moves too far above or below it. Temperature also limits oxygen, because warm water holds less dissolved oxygen than cold water. That is why the same lake fishes differently in March and August, and why a thermometer is useful tackle.

Spawning temperatures from agency pages

The chart shows the active ranges and spawn windows this site works with. Agency figures for spawning, from the Wisconsin DNR: largemouth bass pick nest sites at about 60F and lay eggs at 62 to 65F; smallmouth bass usually spawn at 62 to 64F but have been found spawning at 53F; walleye spawning peaks at 42 to 50F; and bluegill spawn at 67 to 80F, from late May into August. Other states publish somewhat different numbers, and our spawn guide sets them out species by species. Where an agency figure and the chart disagree, go with the agency.

Spawn temperatures →

Trout and warm water

Trout are the clearest case of temperature as a limit. A Vermont Fish and Wildlife Department advisory says trout prefer water in the upper 50s to mid 60s and become increasingly stressed above 70F, when a caught-and-released fish is much more likely to die. Wyoming Game and Fish advises considering keeping your catch, within the regulations, once the water passes 65F and not releasing trout at all once it reaches 70F, which it says is often around noon on hot summer days. Both recommend fishing for warmwater species instead during hot spells, and Wyoming suggests carrying a pocket thermometer.

Trout rivers we cover →

How lakes layer in summer and mix in fall

University of Nebraska extension explains that deep lakes stratify in summer: a warm upper layer sits over a cool deep layer, separated by a thin band, the thermocline, where temperature drops quickly and which stops the two from mixing. The deep layer is where plant material decays, and its dissolved oxygen is often very low, so cool water at depth is not always water fish can use. In fall the surface cools until it is as dense as the bottom water and wind mixes the lake; this turnover spreads oxygen and bottom material through the water, and if it happens too quickly oxygen can drop far enough to kill fish.

USGS gauges guide →

How our reports use temperature

Each water page shows an estimated seasonal water temperature for that type of water, labeled as an estimate, and sorts it into one of four bands: cold (50F or below), cool (51 to 65F), warm (66 to 80F) or hot (above 80F). The band selects the written plan for each species and the suggested baits, and three of the score's rules depend on it. Because the estimate follows the month, it will not drop when a cold front passes; a thermometer at the lake will.

Open any water's report → · Best bass lakes →

Common questions