California, USA
Long-term weather forecast
Long-term weather forecast

May weather forecast and climate
Hercules, CA

Ocean temperature

In Hercules, California, the average seawater temperature in May is 53.1°F (11.7°C).
Note: At temperatures below 50°F (10°C), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 55.4°F (13°C) is not comfortable.


The average length of the day in May in Hercules is 14.3h.

What is the water temperature in May in Hercules?

In Hercules, California, in May, the average water temperature is 53.1°F (11.7°C). Swimming in 53.1°F (11.7°C) is considered life-threatening. Even a few minutes in 55.4°F (13°C) water is uncomfortable, and swimming below 50°F (10°C) may cause total loss of breathing control and cold shock, depending on a person's physique.

What is the average length of the day in May in Hercules?

The average length of the day in May in Hercules, California, is 14.3h.
Average sea temperature in May - Hercules, CA
  • Average sea temperature in May: 53°F

The best month for swimming (with the highest average sea temperature) is September (57°F).
The coldest month (with the lowest average sea temperature) is April (52.6°F).

Average daylight in May - Hercules, CA
  • Average daylight in May: 14.3h

The month with the longest days is June (Average daylight: 14.8h).
The month with shortest days is December (Average daylight: 9.6h).