Lake Harris algae history from satellite

We read Lake Harris from 406 cloud-free satellite scenes between Feb 14, 2016 – Oct 1, 2026. Here is what the surface water showed.

Clear scenes: 406
Typical (median), index: 99
Highest reading: 342 · Apr 8, 2021
Latest scene: 202 · Oct 1, 2026

Algae signal (red-edge index) over time

Algae signal (red-edge index), index. One dot per cloud-free scene; dates are local to the lake.

When it peaks

Month	Clear scenes	Median, index	Scenes rated high
Jan	18	78	67%
Feb	34	110	71%
Mar	38	152	79%
Apr	39	103	51%
May	39	99	41%
Jun	22	100	23%
Jul	36	109	50%
Aug	36	102	78%
Sep	33	92	70%
Oct	40	92	90%
Nov	38	86	87%
Dec	33	78	85%

By year (median / highest): 2016: 57 / 72 (12 scenes) · 2017: 34 / 76 (18 scenes) · 2018: 49 / 86 (37 scenes) · 2019: 62 / 89 (36 scenes) · 2020: 120 / 212 (44 scenes) · 2021: 131 / 342 (45 scenes) · 2022: 98 / 268 (50 scenes) · 2023: 136 / 202 (39 scenes) · 2024: 146 / 301 (37 scenes) · 2025: 96 / 171 (52 scenes) · 2026: 179 / 252 (36 scenes).

What a satellite can and can’t tell you

Satellites see only the surface layer, only on cloud-free days, and only away from the shoreline. They estimate algae; they do not measure toxins, and they can’t see what the lake bottom is doing. A clear reading is not a safety clearance.

For current conditions and health advisories, check the Florida DEP algal bloom page and the Florida Department of Health. If a person or pet may have been exposed to a bloom, call a doctor, a veterinarian, or Poison Help at 1-800-222-1222.

Source: Sentinel-2 MSI (ESA Copernicus), Red-edge cyanobacteria index (CI-cyano); a scene counts as a bloom when the index is above 50 and stays high relative to turbidity (bloom rule v1 (2026-10)). Snapshot exported Oct 9, 2026.

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Month	Clear scenes	Median, index	Scenes rated high
Jan	18	78	67%
Feb	34	110	71%
Mar	38	152	79%
Apr	39	103	51%
May	39	99	41%
Jun	22	100	23%
Jul	36	109	50%
Aug	36	102	78%
Sep	33	92	70%
Oct	40	92	90%
Nov	38	86	87%
Dec	33	78	85%

Month	Clear scenes	Median, index	Scenes rated high
Jan	18	78	67%
Feb	34	110	71%
Mar	38	152	79%
Apr	39	103	51%
May	39	99	41%
Jun	22	100	23%
Jul	36	109	50%
Aug	36	102	78%
Sep	33	92	70%
Oct	40	92	90%
Nov	38	86	87%
Dec	33	78	85%

Month	Clear scenes	Median, index	Scenes rated high
Jan	18	78	67%
Feb	34	110	71%
Mar	38	152	79%
Apr	39	103	51%
May	39	99	41%
Jun	22	100	23%
Jul	36	109	50%
Aug	36	102	78%
Sep	33	92	70%
Oct	40	92	90%
Nov	38	86	87%
Dec	33	78	85%