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Lake Weir algae history from satellite

We read Lake Weir from 409 cloud-free satellite scenes between Apr 14, 2016 – Oct 1, 2026. Here is what the surface water showed.

Clear scenes
409
Typical (median), index
49
Highest reading
140 · May 2, 2024
Latest scene
26 · Oct 1, 2026

Algae signal (red-edge index) over time

0501001502017201820192020202120222023202420252026Apr 14, 2016: 54 index (low)May 14, 2016: 50 index (low)Jun 23, 2016: 94 index (high)Aug 22, 2016: 71 index (low)Sep 11, 2016: 75 index (high)Oct 1, 2016: 86 index (high)Oct 21, 2016: 92 index (high)Nov 10, 2016: 80 index (high)Nov 20, 2016: 74 index (high)Feb 8, 2017: 66 index (high)Mar 30, 2017: 32 index (low)Apr 19, 2017: 47 index (low)May 9, 2017: 33 index (low)May 29, 2017: 73 index (low)Jun 18, 2017: 59 index (low)Jul 3, 2017: 30 index (low)Aug 17, 2017: 25 index (low)Sep 21, 2017: 21 index (low)Sep 26, 2017: 15 index (low)Oct 31, 2017: 17 index (low)Nov 30, 2017: 20 index (low)Dec 10, 2017: 18 index (low)Dec 20, 2017: 27 index (low)Dec 30, 2017: 25 index (low)Jan 4, 2018: 20 index (low)Jan 9, 2018: 22 index (low)Jan 19, 2018: 67 index (low)Feb 18, 2018: 35 index (low)Feb 23, 2018: 43 index (low)Feb 28, 2018: 39 index (low)Mar 5, 2018: 36 index (low)Mar 15, 2018: 33 index (low)Apr 4, 2018: 53 index (low)Apr 14, 2018: 56 index (low)Apr 19, 2018: 48 index (low)Apr 24, 2018: 48 index (low)Apr 29, 2018: 30 index (low)May 4, 2018: 41 index (low)May 9, 2018: 45 index (low)May 24, 2018: 60 index (low)May 29, 2018: 76 index (low)Jun 13, 2018: 62 index (high)Jun 18, 2018: 67 index (high)Jun 23, 2018: 73 index (low)Jul 3, 2018: 62 index (low)Jul 13, 2018: 57 index (low)Aug 2, 2018: 73 index (low)Aug 7, 2018: 49 index (low)Aug 17, 2018: 49 index (low)Aug 27, 2018: 45 index (low)Sep 11, 2018: 51 index (high)Sep 21, 2018: 44 index (low)Sep 26, 2018: 52 index (low)Oct 1, 2018: 57 index (low)Oct 6, 2018: 55 index (high)Oct 16, 2018: 54 index (high)Oct 21, 2018: 40 index (low)Oct 31, 2018: 48 index (low)Dec 5, 2018: 46 index (low)Dec 25, 2018: 56 index (high)Jan 9, 2019: 36 index (low)Jan 24, 2019: 46 index (low)Jan 29, 2019: 37 index (low)Feb 8, 2019: 54 index (high)Feb 23, 2019: 49 index (low)Feb 28, 2019: 59 index (high)Mar 25, 2019: 58 index (low)Apr 4, 2019: 42 index (low)Apr 9, 2019: 62 index (low)Apr 24, 2019: 59 index (high)Apr 29, 2019: 69 index (low)May 9, 2019: 84 index (low)May 19, 2019: 66 index (high)May 24, 2019: 68 index (low)May 29, 2019: 92 index (low)Jun 3, 2019: 88 index (low)Jun 13, 2019: 104 index (low)Jun 23, 2019: 91 index (low)Jun 28, 2019: 82 index (low)Jul 3, 2019: 67 index (low)Jul 23, 2019: 71 index (high)Jul 28, 2019: 73 index (high)Aug 12, 2019: 66 index (low)Aug 22, 2019: 61 index (high)Aug 27, 2019: 56 index (low)Sep 6, 2019: 36 index (low)Sep 11, 2019: 56 index (low)Sep 16, 2019: 63 index (high)Oct 1, 2019: 67 index (high)Oct 11, 2019: 69 index (high)Oct 26, 2019: 84 index (high)Nov 10, 2019: 65 index (high)Nov 20, 2019: 60 index (high)Nov 25, 2019: 59 index (high)Nov 30, 2019: 71 index (high)Dec 5, 2019: 59 index (high)Dec 10, 2019: 81 index (high)Dec 15, 2019: 63 index (high)Dec 20, 2019: 49 index (low)Dec 25, 2019: 74 index (high)Jan 9, 2020: 71 index (high)Feb 3, 2020: 46 index (low)Feb 8, 2020: 52 index (high)Feb 13, 2020: 61 index (low)Feb 23, 2020: 60 index (high)Feb 28, 2020: 51 index (high)Mar 4, 2020: 69 index (high)Mar 14, 2020: 111 index (high)Mar 19, 2020: 78 index (high)Mar 29, 2020: 69 index (high)Apr 3, 2020: 50 index (low)Apr 13, 2020: 62 index (low)Apr 23, 2020: 55 index (low)Apr 28, 2020: 51 index (low)May 3, 2020: 46 index (low)May 8, 2020: 43 index (low)May 13, 2020: 62 index (low)Jun 17, 2020: 40 index (low)Jul 12, 2020: 29 index (low)Jul 17, 2020: 46 index (low)Jul 22, 2020: 62 index (low)Jul 27, 2020: 33 index (low)Aug 1, 2020: 30 index (low)Aug 16, 2020: 34 index (low)Aug 26, 2020: 40 index (low)Sep 5, 2020: 25 index (low)Sep 10, 2020: 29 index (low)Sep 25, 2020: 25 index (low)Sep 30, 2020: 13 index (low)Oct 10, 2020: 54 index (low)Oct 15, 2020: 23 index (low)Oct 25, 2020: 24 index (low)Oct 30, 2020: 13 index (low)Nov 4, 2020: 21 index (low)Nov 14, 2020: 27 index (low)Nov 24, 2020: 20 index (low)Dec 9, 2020: 18 index (low)Dec 14, 2020: 40 index (low)Dec 19, 2020: 25 index (low)Dec 29, 2020: 20 index (low)Jan 18, 2021: 21 index (low)Jan 28, 2021: 22 index (low)Feb 2, 2021: 31 index (low)Feb 7, 2021: 30 index (low)Feb 12, 2021: 38 index (low)Feb 22, 2021: 34 index (low)Feb 27, 2021: 37 index (low)Mar 4, 2021: 29 index (low)Mar 9, 2021: 32 index (low)Mar 14, 2021: 39 index (low)Mar 19, 2021: 36 index (low)Mar 24, 2021: 40 index (low)Apr 3, 2021: 42 index (low)Apr 8, 2021: 55 index (low)Apr 13, 2021: 50 index (low)Apr 23, 2021: 64 index (low)Apr 28, 2021: 79 index (low)May 3, 2021: 67 index (low)May 8, 2021: 69 index (high)May 18, 2021: 106 index (low)May 28, 2021: 90 index (high)Jun 12, 2021: 86 index (low)Jun 22, 2021: 82 index (low)Jun 27, 2021: 82 index (low)Jul 2, 2021: 56 index (low)Jul 12, 2021: 44 index (low)Jul 17, 2021: 48 index (low)Jul 22, 2021: 45 index (low)Jul 27, 2021: 54 index (low)Aug 11, 2021: 46 index (low)Aug 21, 2021: 34 index (low)Sep 10, 2021: 24 index (low)Sep 15, 2021: 39 index (low)Sep 25, 2021: 35 index (low)Sep 30, 2021: 27 index (low)Oct 10, 2021: 34 index (low)Oct 15, 2021: 35 index (low)Oct 20, 2021: 28 index (low)Oct 30, 2021: 32 index (low)Nov 9, 2021: 30 index (low)Nov 14, 2021: 20 index (low)Nov 24, 2021: 25 index (low)Nov 29, 2021: 23 index (low)Dec 4, 2021: 23 index (low)Dec 14, 2021: 53 index (low)Dec 24, 2021: 25 index (low)Dec 29, 2021: 32 index (low)Jan 3, 2022: 25 index (low)Jan 8, 2022: 31 index (low)Jan 13, 2022: 32 index (low)Jan 18, 2022: 30 index (low)Feb 2, 2022: 30 index (low)Feb 12, 2022: 36 index (low)Feb 22, 2022: 36 index (low)Feb 27, 2022: 44 index (low)Mar 4, 2022: 35 index (low)Mar 14, 2022: 41 index (low)Mar 19, 2022: 41 index (low)Mar 29, 2022: 33 index (low)Apr 3, 2022: 33 index (low)Apr 8, 2022: 36 index (low)May 8, 2022: 71 index (low)May 13, 2022: 59 index (high)May 18, 2022: 77 index (high)May 28, 2022: 60 index (low)Jun 2, 2022: 69 index (low)Jun 7, 2022: 64 index (high)Jun 12, 2022: 97 index (low)Jun 17, 2022: 64 index (low)Jul 7, 2022: 51 index (high)Jul 12, 2022: 60 index (low)Jul 17, 2022: 49 index (low)Jul 22, 2022: 48 index (low)Jul 27, 2022: 46 index (low)Aug 1, 2022: 36 index (low)Aug 6, 2022: 49 index (low)Aug 16, 2022: 31 index (low)Aug 21, 2022: 36 index (low)Aug 26, 2022: 38 index (low)Sep 5, 2022: 33 index (low)Sep 15, 2022: 34 index (low)Sep 20, 2022: 34 index (low)Sep 25, 2022: 36 index (low)Sep 30, 2022: 31 index (low)Oct 5, 2022: 27 index (low)Oct 10, 2022: 23 index (low)Oct 15, 2022: 29 index (low)Oct 20, 2022: 23 index (low)Oct 25, 2022: 31 index (low)Oct 30, 2022: 32 index (low)Nov 4, 2022: 37 index (low)Nov 14, 2022: 38 index (low)Nov 24, 2022: 46 index (low)Nov 29, 2022: 27 index (low)Dec 4, 2022: 37 index (low)Dec 9, 2022: 42 index (low)Dec 14, 2022: 44 index (low)Dec 19, 2022: 28 index (low)Dec 24, 2022: 29 index (low)Dec 29, 2022: 30 index (low)Jan 8, 2023: 32 index (low)Jan 28, 2023: 24 index (low)Feb 7, 2023: 32 index (low)Feb 17, 2023: 38 index (low)Feb 22, 2023: 42 index (low)Mar 4, 2023: 52 index (low)Mar 9, 2023: 40 index (low)Mar 14, 2023: 38 index (low)Mar 19, 2023: 41 index (low)Mar 24, 2023: 42 index (low)Mar 29, 2023: 43 index (low)Apr 18, 2023: 45 index (low)Apr 23, 2023: 57 index (low)May 3, 2023: 58 index (low)May 8, 2023: 67 index (high)May 13, 2023: 102 index (low)May 18, 2023: 80 index (high)May 28, 2023: 56 index (low)Jun 7, 2023: 86 index (low)Jun 12, 2023: 104 index (low)Jun 27, 2023: 90 index (low)Jul 2, 2023: 79 index (high)Jul 12, 2023: 70 index (high)Aug 11, 2023: 68 index (high)Aug 16, 2023: 74 index (low)Aug 21, 2023: 70 index (low)Aug 26, 2023: 74 index (high)Sep 10, 2023: 63 index (high)Sep 15, 2023: 71 index (high)Sep 25, 2023: 60 index (high)Oct 5, 2023: 69 index (high)Oct 15, 2023: 46 index (low)Oct 20, 2023: 56 index (high)Oct 30, 2023: 60 index (high)Nov 4, 2023: 54 index (high)Nov 9, 2023: 65 index (high)Nov 19, 2023: 51 index (high)Nov 29, 2023: 41 index (low)Dec 9, 2023: 52 index (high)Dec 19, 2023: 40 index (low)Jan 28, 2024: 51 index (high)Feb 2, 2024: 49 index (low)Feb 7, 2024: 51 index (high)Feb 12, 2024: 52 index (low)Feb 22, 2024: 48 index (low)Mar 3, 2024: 84 index (high)Mar 23, 2024: 78 index (high)Apr 7, 2024: 66 index (high)Apr 12, 2024: 79 index (low)Apr 17, 2024: 72 index (low)Apr 22, 2024: 97 index (high)May 2, 2024: 140 index (high)May 7, 2024: 123 index (high)May 22, 2024: 104 index (low)May 27, 2024: 117 index (low)Jun 6, 2024: 106 index (high)Jun 16, 2024: 102 index (high)Jun 21, 2024: 108 index (low)Jun 26, 2024: 105 index (high)Jul 1, 2024: 92 index (high)Jul 6, 2024: 88 index (low)Jul 16, 2024: 66 index (high)Jul 21, 2024: 54 index (high)Jul 26, 2024: 52 index (low)Aug 10, 2024: 66 index (low)Aug 15, 2024: 59 index (low)Aug 20, 2024: 45 index (low)Aug 25, 2024: 39 index (low)Aug 30, 2024: 43 index (low)Sep 24, 2024: 35 index (low)Oct 4, 2024: 49 index (low)Oct 14, 2024: 33 index (low)Oct 19, 2024: 42 index (low)Oct 24, 2024: 39 index (low)Oct 29, 2024: 29 index (low)Nov 3, 2024: 41 index (low)Nov 13, 2024: 37 index (low)Nov 18, 2024: 31 index (low)Nov 23, 2024: 32 index (low)Nov 28, 2024: 35 index (low)Dec 3, 2024: 33 index (low)Dec 13, 2024: 37 index (low)Dec 28, 2024: 43 index (low)Jan 12, 2025: 32 index (low)Jan 17, 2025: 29 index (low)Feb 6, 2025: 45 index (low)Feb 21, 2025: 39 index (low)Feb 26, 2025: 38 index (low)Mar 3, 2025: 40 index (low)Mar 13, 2025: 42 index (low)Mar 18, 2025: 30 index (low)Mar 28, 2025: 40 index (low)Apr 2, 2025: 65 index (low)Apr 7, 2025: 46 index (low)Apr 12, 2025: 49 index (low)Apr 17, 2025: 46 index (low)May 7, 2025: 114 index (high)May 9, 2025: 74 index (high)May 17, 2025: 63 index (low)May 27, 2025: 81 index (low)May 29, 2025: 79 index (high)Jun 1, 2025: 62 index (low)Jun 6, 2025: 69 index (low)Jun 16, 2025: 61 index (low)Jun 18, 2025: 84 index (low)Jun 21, 2025: 48 index (low)Jul 1, 2025: 59 index (low)Jul 6, 2025: 80 index (low)Jul 11, 2025: 74 index (high)Jul 26, 2025: 61 index (low)Jul 28, 2025: 71 index (high)Jul 31, 2025: 85 index (high)Aug 5, 2025: 50 index (low)Aug 15, 2025: 59 index (high)Aug 20, 2025: 71 index (low)Sep 6, 2025: 65 index (high)Sep 14, 2025: 51 index (low)Sep 19, 2025: 61 index (high)Sep 24, 2025: 65 index (high)Sep 26, 2025: 76 index (high)Sep 29, 2025: 68 index (high)Oct 14, 2025: 67 index (high)Oct 16, 2025: 64 index (high)Oct 19, 2025: 64 index (high)Oct 24, 2025: 53 index (high)Nov 3, 2025: 48 index (low)Nov 5, 2025: 61 index (high)Nov 8, 2025: 80 index (high)Nov 13, 2025: 52 index (high)Nov 18, 2025: 74 index (high)Nov 23, 2025: 71 index (low)Nov 25, 2025: 101 index (high)Nov 28, 2025: 57 index (high)Dec 8, 2025: 84 index (low)Dec 13, 2025: 62 index (high)Dec 23, 2025: 57 index (high)Jan 7, 2026: 67 index (high)Jan 17, 2026: 11 index (low)Jan 22, 2026: 17 index (low)Jan 27, 2026: 36 index (low)Feb 1, 2026: 35 index (low)Feb 6, 2026: 32 index (low)Feb 21, 2026: 34 index (low)Feb 26, 2026: 29 index (low)Mar 3, 2026: 22 index (low)Mar 8, 2026: 50 index (high)Mar 15, 2026: 52 index (low)Mar 18, 2026: 22 index (low)Mar 28, 2026: 34 index (low)Apr 2, 2026: 26 index (low)Apr 4, 2026: 37 index (low)Apr 12, 2026: 23 index (low)Apr 17, 2026: 30 index (low)Apr 24, 2026: 36 index (low)Apr 27, 2026: 67 index (low)May 7, 2026: 37 index (low)May 17, 2026: 66 index (low)Jun 6, 2026: 43 index (low)Jun 11, 2026: 46 index (low)Jun 26, 2026: 39 index (low)Jul 1, 2026: 38 index (low)Jul 11, 2026: 7.3 index (low)Aug 5, 2026: 29 index (low)Aug 15, 2026: 31 index (low)Aug 20, 2026: 27 index (low)Aug 30, 2026: 30 index (low)Sep 4, 2026: 44 index (low)Sep 14, 2026: 37 index (low)Oct 1, 2026: 26 index (low)
Algae signal (red-edge index), index. One dot per cloud-free scene; dates are local to the lake.

When it peaks

MonthClear scenesMedian, indexScenes rated high
Jan223114%
Feb353920%
Mar344021%
Apr38508%
May386832%
Jun328222%
Jul355731%
Aug354611%
Sep343832%
Oct394236%
Nov354643%
Dec324025%

By year (median / highest): 2016: 75 / 94 (9 scenes) · 2017: 27 / 73 (15 scenes) · 2018: 49 / 76 (36 scenes) · 2019: 64 / 104 (40 scenes) · 2020: 41 / 111 (40 scenes) · 2021: 37 / 106 (47 scenes) · 2022: 36 / 97 (53 scenes) · 2023: 57 / 104 (40 scenes) · 2024: 52 / 140 (43 scenes) · 2025: 62 / 114 (53 scenes) · 2026: 34 / 67 (33 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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