Lake St. Clair smallmouth by month: lake temperature and season
How warm Lake St. Clair usually is in each month, and the season phase the app gives that water. From the daily lake-average surface temperature of NOAA (the National Oceanic and Atmospheric Administration), GLSEA (the Great Lakes Surface Environmental Analysis), for 1995-2025: 31 years, 11,323 days.
Lake temperature and season phase by month
| Month | Lake temperature: median (10th-90th percentile) | Season phase, share of days | Target depth of the most common phase |
|---|---|---|---|
| January | 32.4 F (32.4-36.0 F) | Winter 100% | 18-27 ft (winter) |
| February | 32.4 F (32.4-34.2 F) | Winter 100% | 18-27 ft (winter) |
| March | 32.4 F (32.4-40.1 F) | Winter 98% | 18-27 ft (winter) |
| April | 44.2 F (37.8-49.1 F) | Winter 58%, pre-spawn 42% | 18-27 ft (winter) |
| May | 55.5 F (48.9-61.3 F) | Pre-spawn 72%, spawn 25% | 8-16 ft (pre-spawn) |
| June | 66.9 F (60.8-71.6 F) | Spawn 43%, post-spawn 32%, summer 22% | 3-10 ft (spawn) |
| July | 73.8 F (70.3-77.1 F) | Summer 92%, post-spawn 8% | 15-24 ft (summer) |
| August | 74.1 F (71.1-77.4 F) | Summer 100% | 15-24 ft (summer) |
| September | 69.0 F (63.7-73.3 F) | Summer 68%, early fall 31% | 15-24 ft (summer) |
| October | 57.4 F (51.4-64.8 F) | Late fall 54%, early fall 44% | 16-22 ft (late fall) |
| November | 46.1 F (39.9-51.5 F) | Late fall 60%, winter 40% | 16-22 ft (late fall) |
| December | 37.1 F (32.4-42.3 F) | Winter 98% | 18-27 ft (winter) |
Median: half of the month's days were warmer and half colder. 10th-90th percentile: 8 days in 10 were in this range. The phase share counts the days on which the rules below give each phase, from that day's lake temperature and its change over the 7 days before; phases on fewer than 5% of a month's days are not listed. From December to March many readings are 32.4 F, GLSEA's value for ice or its lowest analysis value, not a measured water temperature.
The phase rules
The first rule that fits decides. Warming means the lake temperature rose, or stayed the same, over the last 7 days.
- Winter: below 45 F, any date.
- Pre-spawn: 45 to below 58 F and warming, March 1 to June 30.
- Spawn: 58 to below 68 F and warming, May 1 to June 30.
- Post-spawn: 58 to below 70 F, May 1 to July 14.
- Summer: July 15 to Sept 15, or 68 F and warmer from July 1.
- Early fall: 58 to below 68 F and cooling, Sept 1 to Nov 30.
- Late fall: below 58 F and cooling, Oct 1 to Dec 31.
A day that no rule fits gets its phase from the temperature alone. The temperature limits and the date windows are starting values, from published ranges, the tournament record or engineering judgment. The depth bands of post-spawn, summer and early fall rest on published reports; those of winter, pre-spawn, spawn and late fall are starting values. The app's tournament backtest and anglers' logbooks are used to check and calibrate these values. Fishing seasons and limits are separate from the phases: see Bass season dates 2027.
Sources and related pages
- Lake temperature: NOAA Great Lakes Environmental Research Laboratory, GLSEA lake-average surface temperature, Lake St. Clair, daily, 1995-2025 (public domain).
- Phase rules and depth bands: Lake St. Clair's values in the app, the same the plan uses.
- Fish and temperature: the phase rules, all depth bands with their evidence, and a calculator
- Water temperature: how the app projects the lake temperature for a plan
- Lake St. Clair areas: depth and bottom of each area
- Plan: today's phase and the areas ranked for your boat and limits