Moving north will absolutely wreck your SAD (especially in late winter)

Moving from a low-latitude to a high-latitude region significantly worsens both the onset and severity of SAD, and late winter is where it hits hardest.

Here’s why: your body has been trained on consistent, strong daylight year-round. Low-latitude places have minimal seasonal variation — roughly 12 hours of daylight all year. Move to, say, Seattle or Stockholm, and suddenly you’re looking at 6–7 hours of weak, angled winter sun. Your brain never had to deal with that before. There’s no adaptation buffer.

The real kicker is timing. SAD onset typically ramps up in fall and peaks in late winter (January through March) because that’s when the cumulative light deficit is biggest and you’ve been starved for months.