Is there a jellyfish season in San Diego, and how do you treat a sting?
Mostly summer and early fall, when warm water pushes them in. Purple-striped jellies are around all year and sting hardest. For a sting: rinse with seawater, pull off tentacles, then use heat. Skip the vinegar.
- Worst months
- Summer–fall
- Strongest sting
- Purple-striped
- Treatment
- Heat
- Vinegar
- Skip it
Warm water and currents
Painful, not life-threatening
About 106–113°F water
Can worsen sea nettle stings
The short version
- Purple-striped jellies are found off San Diego year-round, usually without large surface blooms, and have a strong, painful sting.
- Black sea nettles are rare visitors in unusually warm summers; Scripps counted only about six appearances in a century as of 2007.
- Blue "by-the-wind sailors" (Velella) wash up in spring and fall and are harmless to people.
- Big sting days happen in warm summers: 135 people were stung at Encinitas in one weekend in July 2012.
- The Red Cross no longer recommends vinegar for most U.S. coastal stings; rinse with seawater, remove tentacles and use hot water.
San Diego doesn't have a jellyfish season the way it has a stingray season, but warm water and shifting currents bring them closer to shore in summer and early fall. Most of the time you'll never see one. When you do, it helps to know which one you're looking at.
The jellies you might meet
| Jelly | When | Sting |
|---|---|---|
| Purple-striped jelly | Year-round, more in warm months | Strong and very painful, not life-threatening |
| Black sea nettle | Rare; unusually warm summers | Mild to moderate, like a bee sting |
| Pacific sea nettle | Occasional | Moderate |
| Moon jelly | Washes up periodically | Mild |
| By-the-wind sailor (Velella) | Late spring and early fall | Harmless to people |
If you're stung
- 01
Rinse with seawater
Not fresh water, which can make leftover stinging cells fire.
- 02
Remove tentacles carefully
Scrape or pick them off without rubbing; use a card edge or gloves.
- 03
Apply heat
Hot water around 106–113°F, or a hot pack, as hot as you can tolerate. A cold pack is a fallback if there's no heat.
- 04
Tell a lifeguard
They can treat it and will know if others are getting stung that day.
SOURCES
Everything above traces back to one of these. Follow them — if one has changed and we haven't, that's our mistake, not yours.
Scripps Institution of Oceanography Zooplankton Guide · Checked October 6, 2026
Year-round presence, strong sting
- BackgroundJellyfish (black sea nettle)
Scripps Institution of Oceanography · September 1, 2007
Rare warm-water visitor
American Red Cross Scientific Advisory Council · June 2016
Vinegar and heat guidance
- BackgroundBeach safety tips
Scripps Health · June 4, 2026
Seawater rinse, heat, lifeguard
KPBS · July 16, 2012
Encinitas sting event
Axios San Diego · April 30, 2024
By-the-wind sailors