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Tomales Bay in May 2027: darkest nights

Night kayak tours from Marshall and Inverness. Fog helps; moonlight hurts. Late summer to early autumn.

7 pitch-dark nights, 9 dark nights

New moon Thu 6 May · Full moon Thu 20 May

Night by night, May 2027

NightMoon20:0021:30Best
Sat 1 May 19%●●●●●●●●●●21:30
Sun 2 May 12%●●●●●●●●●●21:30
Mon 3 May 6%●●●●●●●●●●21:30
Tue 4 May 2%●●●●●●●●●●21:30
Wed 5 May 0%●●●●●●●●●●21:30
Thu 6 May 1%●●●●●●●●●●21:30
Fri 7 May 4%●●●●●●●●●●21:30
Sat 8 May 10%●●●●●●●●●●21:30
Sun 9 May 18%●●●●●●●●●●21:30
Mon 10 May 28%●●●●●●●●●●21:30
Tue 11 May 39%●●●●●●●●●●21:30
Wed 12 May 51%●●●●●●●●●●21:30
Thu 13 May 62%●●●●●●●●●●21:30
Fri 14 May 73%●●●●●●●●●●21:30
Sat 15 May 82%●●●●●●●●●●21:30
Sun 16 May 90%●●●●●●●●●●21:30
Mon 17 May 95%●●●●●●●●●●21:30
Tue 18 May 99%●●●●●●●●●●21:30
Wed 19 May 100%●●●●●●●●●●21:30
Thu 20 May 99%●●●●●●●●●●21:30
Fri 21 May 96%●●●●●●●●●●21:30
Sat 22 May 92%●●●●●●●●●●21:30
Sun 23 May 86%●●●●●●●●●●21:30
Mon 24 May 79%●●●●●●●●●●21:30
Tue 25 May 71%●●●●●●●●●●21:30
Wed 26 May 62%●●●●●●●●●●21:30
Thu 27 May 52%●●●●●●●●●●21:30
Fri 28 May 43%●●●●●●●●●●21:30
Sat 29 May 33%●●●●●●●●●●21:30
Sun 30 May 24%●●●●●●●●●●21:30
Mon 31 May 15%●●●●●●●●●●21:30

Check one night in detail Tomales Bay tours

Questions

What are the best nights to see the bioluminescence at Tomales Bay in May 2027?

The darkest nights are Sat 1 May, Sun 2 May, Mon 3 May, Tue 4 May, Wed 5 May, Thu 6 May, Fri 7 May. 9 of 31 nights score at least 4 out of 5.

Which nights should I avoid in May 2027?

Avoid the nights around the full moon on Thu 20 May, when moonlight washes out the glow.

20:00 or 21:30: which Tomales Bay tour is darker in May?

20:00 is the darker choice on 0 nights; 21:30 is the darker choice on 20 nights.

Tomales Bay darkness by month

Darkness score 1-5 per tour slot from twilight and moonlight. Weather and plankton health are not included. Times are local (America/Los_Angeles).