Swimmers could experience hypothermia in only 30 minutes off the coast of Crescent City, California, after water temperatures plunged because of coastal winds.

Summer temperatures in Northern and Central California could have more people flocking to the beach to cool off in the ocean, but data from the National Oceanic and Atmospheric Administration shows that some of the coastal waters are too cold for safe swimming. A recent temperature reading off the coast of Crescent City revealed that water temperatures were 47.3 degrees Fahrenheit, more than 3 degrees below normal for this time of year and 4 degrees below winter water temperatures in January.

Meteorologists and weather experts are blaming the temperature plunge on an "intense marine cold spell."