When is allergy season in San Francisco? Pollen can be present across much of the year, with trees becoming more prominent in winter and spring, grasses in spring and summer, and weeds later in summer and fall. California’s warmer climate can also stretch some pollen seasons beyond the typical national timeline.
San Francisco weather has never been particularly interested in following the seasons. Pollen can be similar.
While other cities may have a more recognizable spring-to-fall allergy calendar, Bay Area allergies don’t always stay inside the usual seasonal lines. Tree pollen can get an early start, grasses can stick around and changing weather can shift when different pollen types become more noticeable.
Think less “allergy season starts now” and more “what’s in the air right now?”
Here’s why San Francisco’s pollen calendar can be unusually long, how Bay Area allergies show up throughout the year and how to keep your routine ready when conditions change.
Does San Francisco have a typical allergy season?
Not exactly. San Francisco can experience seasonal pollen across much of the year, with tree pollen potentially starting in winter and other pollen types following through spring, summer and fall.
Across the US, tree pollen is typically most prominent from February through April, but warmer regions can see it as early as December or January. Grass pollen follows in spring and summer, while weed pollen becomes more common later in the year.
A general timeline looks like this:
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Winter into spring: Tree pollen
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Spring into summer: Grass pollen
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Late summer into fall: Weed pollen
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Throughout the year: Indoor allergens like dust mites, pet allergens and mold
If you want the pollen basics first, explore our guide to pollen season.
Which pollen is common in San Francisco?
The pollen you encounter changes throughout the year, with trees typically appearing first, followed by grasses and weeds.
Trees: Winter and spring
Common allergy-triggering trees nationally include alder, ash, birch, cedar, cypress, elm, juniper, maple, oak and olive.
Which species matter most depends on what's growing around you and your individual sensitivities.
For some noses, spring blooms are less “look how pretty” and more “look what just happened to my pollen forecast.”
Grasses: Spring and summer
Grass pollen becomes more prominent as temperatures warm. Common allergy-triggering grasses include Bermuda, fescue, Kentucky blue, orchard, rye and Timothy grass.
The Asthma and Allergy Foundation of America (AAFA) notes that grass pollen can stick around for longer periods in warmer areas like California, which can help explain why SF allergies don't always fit neatly into a short spring window.
Weeds: Late summer and fall
Later in the year, weed pollen becomes more relevant. Potential triggers include pigweed, sagebrush, mugwort and ragweed, although individual species vary significantly by location.
Instead of guessing what's responsible, checking local pollen conditions can tell you which category is actually elevated.
Why can Bay Area allergy season last so long?
Bay Area allergy season can extend across much of the year because different plants pollinate at different times and California’s relatively mild climate can lengthen some pollen seasons.
Weather adds another variable.
That can make a calendar-based approach tricky. A month that was relatively quiet one year may look different the next depending on temperature, rainfall and wind.
And San Francisco has another familiar complication: conditions can change quickly. Your morning may start cool and foggy while another part of the Bay Area is warmer and drier. Rather than assuming a certain month means a certain pollen level, current local conditions can give you a more useful snapshot.
Wind can carry pollen significant distances, so the plant bothering you doesn’t necessarily need to be growing outside your apartment. Temperature and rainfall can also affect when plants grow and release pollen.
The important part: your pollen calendar can change from one year to the next.
Why your San Francisco allergy season may look different from someone else’s
Your personal allergy season depends less on one “worst” month and more on which pollen types you're sensitive to.
Someone sensitive to tree pollen may pay more attention to winter and spring. Grass sensitivities can make spring and summer stand out while weed pollen may become more relevant later in summer and fall.
That means two people can check the same San Francisco pollen forecast and have very different days.
Seasonal pollen allergies can include a stuffy or runny nose, sneezing, postnasal drip, itchy eyes, nose, ears or mouth and red or watery eyes.
Learn more in our guide to indoor allergies.
How can you prepare for high-pollen days in San Francisco?
You can’t negotiate with the pollen forecast. You can make it part of your daily planning.
Know what's in the air
Check local pollen conditions before a long walk, park afternoon or outdoor workout. Look at whether tree, grass or weed pollen is elevated rather than relying only on the overall number.
Knowing your individual triggers can make that forecast even more useful.
Keep pollen from settling in
Pollen can travel home on clothes, shoes and hair.
During higher-pollen periods, keeping windows closed and changing clothes after extended outdoor time can help limit what gets tracked inside.
Fog outside. Pollen outside. Ideally, both stay there.
Give your nose a cleansing step
After a day of breathing in whatever the Bay Area has floating around, your nose could use a little reset.
For regular upkeep, Sinus Rinse Free + Clear offers a gentle daily cleanse to wash away mucus and allergens while helping hydrate and comfort nasal passages. Its Activated Saline™ formula also includes prebiotics and postbiotics to support a healthy nasal microbiome.
Need something more thorough? Advanced Sinus Rinse Free + Clear is made for a deeper cleanse of mucus and allergens, with convenient single-dose pouches and a reusable Nasal Pillow applicator.
Whether it’s everyday maintenance or a deeper rinse kind of day, there’s an easy way to make nasal cleansing part of your routine.
When allergy season lasts longer, think routine over reaction
In a place where pollen doesn't always stick to one tidy season, nasal wellness doesn't have to wait for a certain month either.
At Wizard Wellness, we put the nasal microbiome at the center of everyday nasal wellness. Think of it like skincare for your nose: a simple routine that fits into what you're already doing.
After extended time outdoors, a nasal rinse can help cleanse pollen, dust and other particles from the nasal passages. Daily Nasal Spray can follow as a refreshing everyday step.
Wizard's proprietary Nasalbiome™ Technology is designed to support a balanced nasal microbiome, bringing approachable science to a part of your wellness routine that deserves a little more attention.
Wondering what a nasal microbiome actually is? Our guide to the nasal microbiome breaks it down.
San Francisco may not give you a perfectly predictable allergy season. Your routine can still be ready for it.
So, when is allergy season in San Francisco?
When is allergy season in San Francisco? It can stretch across much of the year. Tree pollen can appear during winter and spring, grass becomes more prominent in spring and summer then weeds contribute later in summer and fall.
The Bay Area's milder climate means those windows aren't always as tidy as they might be elsewhere.
Rather than waiting for allergy season to officially “start,” get familiar with your triggers, watch current pollen conditions and keep a simple nasal wellness routine ready when levels rise.
Because in San Francisco, layers aren't just for the weather.
Shop the Allergy Season Survival Ritual
Frequently asked questions
What month is pollen highest in San Francisco?
There isn't one peak month for every pollen type. Tree, grass and weed pollen become prominent at different times, and weather can shift their timing from year to year.
What pollen is common in San Francisco?
Tree pollen is generally more prominent earlier in the year, followed by grasses then weeds. Potential triggers include oak, alder, cypress and olive trees, grasses such as Bermuda and rye and weeds including pigweed and sagebrush.
Why are my allergies so bad in the Bay Area?
Different pollen seasons can overlap, while California's warmer climate can allow some pollen to remain present beyond traditional seasonal windows. Weather can also influence how much pollen becomes airborne.
Can you have seasonal allergies year-round in San Francisco?
Certain pollen can be present for extended periods in warmer climates. The Asthma and Allergy Foundation of America (AAFA) notes that grass pollen may be found year-round in warmer areas including California. Year-round symptoms can also be associated with indoor allergens, so persistent symptoms are worth discussing with a healthcare professional.