Vitamin DGlobal Solar Explorer

Vitamin D from the sun in Seattle

In Seattle you can synthesize vitamin D from March to September.

From October to February synthesis isn't possible — this is when a supplement can help.

More precisely: March 11 – October 9.

Year-round profile in Seattle

JFMAMJJASOND
Daily hours with enough sun to synthesize vitamin D across the year.

Seasonal windows

  • March: between 11:00 and 14:00, about 15 min for 1000 IU.
  • June: between 09:00 and 17:00, about 7 min for 1000 IU.
  • September: between 10:00 and 15:00, about 13 min for 1000 IU.
  • December: synthesis isn't possible.

Estimated for Fitzpatrick type III skin, arms and face exposed, clear sky.

When to supplement in Seattle

During the months without solar synthesis, vitamin D comes only from food or a supplement. It is usually taken as D3, often with magnesium — which the body needs to activate it — and vitamin K (as K2), which contributes to the maintenance of normal bones.

Calculate my window in Seattle

Frequently asked questions about vitamin D in Seattle

Can I get vitamin D from the sun in winter in Seattle?
In Seattle you can synthesize vitamin D from March to September.
How many minutes of sun do I need in Seattle?
In summer, about 15 minutes with arms and face exposed is enough for 1000 IU (Fitzpatrick type III skin, clear sky).
Built by Javier Aguilar