Do My Health Scores Change With the Seasons?
Published · 7 min read
Yes, and the size of the shift is close enough to your device's own alert threshold to matter.
If your readiness or recovery score has been quietly worse for a few weeks and nothing in your life explains it, the calendar is a real candidate. Seasonal change moves resting heart rate, heart-rate variability and sleep architecture in measurable ways. Most people meet this as a run of mildly disappointing mornings with no obvious cause.
This guide does something narrow. It looks at what the wearable makers have published from their own users, what the peer-reviewed wearable literature found, and where the two disagree. Every figure below is quoted from its source and linked. Where a source does not say, or contradicts itself, that is recorded rather than smoothed over.
The short answer, in a table
| Metric | Direction in winter | Best available source |
|---|---|---|
| Resting or nighttime heart rate | Higher | Oura community data; Vazquez et al. 2026 |
| Nighttime HRV | Lower | Oura community data |
| Time in bed | Longer | Oura community data |
| Deep sleep share | Lower | Oura community data |
| REM sleep share | Higher | Oura community data |
The summer column is the mirror of it. Note that every row runs the same way: winter looks, to a score, like a worse version of you.
Oura published six findings from its own users, and admitted what it could not explain
Oura's analysis of its own community (ouraring.com) lists what changes in summer relative to winter:
- Time spent in bed decreases
- The % of REM sleep decreases
- The % of deep sleep increases
- Nighttime HRV averages trend higher
- Nighttime heart rate averages run lower
- Nighttime respiration rates are higher
The sleep-architecture half has a mundane explanation, and Oura's lead scientist Heli Koskimäki gives it:
"When temperatures rise and it's lighter for longer outside, we tend to spend less time in bed, cutting our total sleep time short. When we sleep less, we shift the balance of our sleep stages towards deep sleep and away from REM sleep which tends to occur more in later sleep cycles."
So the deep-sleep and REM numbers are mostly a consequence of total sleep time, not a separate seasonal effect. That is worth knowing before you read a summer deep-sleep rise as an improvement.
The cardiovascular half is the interesting part, because Koskimäki declines to explain it:
"The changes in our heart rate, respiration, and HRV, however, are more mysterious."
That is a vendor publishing a finding from its own data and saying plainly that it does not know the mechanism. It is the honest position, and it is rarer than it should be.
The peer-reviewed number, and who it came from
The clearest published figure comes from a 2026 study in the Journal of Biological Rhythms (journals.sagepub.com), which analysed wearable sleep studies rather than laboratory visits:
"We conducted a retrospective analysis of 2,386 home sleep studies, one study per individual, recorded between 2022 and 2025 using the SleepImage wearable system in Fresno, California."
Its heart-rate result:
"Mean heart rate was higher in winter (68.3 ± 10.9 bpm) compared with summer (65.7 ± 9.3 bpm, p < 0.001)."
Read the population before you read the number. These are clinical home sleep studies in a single Californian city, one per person, not a healthy general cohort and not a year-long record of the same individuals. It is strong evidence that the effect is real and measurable at scale. It is not a prediction of the exact gap in your own data, and anyone quoting 2.6 bpm as though it were your personal seasonal swing is overreading it.
Why 2.6 beats per minute is not a trivial number
Here is the part that connects the research to your morning screen.
The winter-to-summer gap in that study is 2.6 bpm. Now compare it against the threshold your device uses to decide something is wrong. Oura's own documentation on resting heart rate (support.ouraring.com, last updated 14 July 2026) says:
"Variation beyond 3-5 BPM above or below your personal average may be a sign of low recovery or excessive stress on your body, such as illness, poor diet choices, late-night eating, or lack of sleep."
And, more concretely:
"You'll observe decreased Readiness Scores if you receive an RHR that is 10-15 BPM lower than usual, as well as if you receive an RHR that is 3-5 BPM higher than usual."
So a population-level seasonal shift of 2.6 bpm sits just under the 3-5 bpm band that costs you Readiness points. It does not take much of an individual swing on top of that to cross it. Nothing has gone wrong with you, and nothing has gone wrong with the device. The season moved, and the comparison did not move with it.
The list of causes in that Oura quotation is worth rereading too. Illness, diet, late eating, poor sleep. The season is not on it.
Where the literature does not agree, stated plainly
It would be tidier to claim the science is settled. It is not, and the disagreement is old.
A 2000 study of 24-hour heart-rate variability in 120 healthy men (academic.oup.com) reports, in its Results:
"Although there were no seasonal differences in mean R-R interval, all indexes of HRV were found to be lower in the summer than they were during winter."
Mean R-R interval is the inverse of mean heart rate, so that paper found no seasonal heart-rate difference at all, which is the opposite of the 2026 wearable finding. And on HRV its own abstract contradicts itself: the Results say HRV was lower in summer, while the Conclusions of the same abstract say values were lowest in winter.
Two honest readings follow. The heart-rate direction has better and more recent evidence behind it, from a far larger sample measured at home rather than in a clinic. The HRV direction is genuinely unresolved in the sources available without a paywall, and this guide will not pretend otherwise. If you see a confident seasonal HRV claim quoted without a population, treat it carefully.
The real problem is the window your baseline is built from
Every point above is about population averages. The thing that actually produces your score is narrower, and it is where seasonality bites.
Oura describes its comparison window as a long-term average "collected over the past ~ 2 months" (support.ouraring.com). Most devices work on something similar, which is the subject of how long until my baseline is accurate.
Now consider what a two-month window does in late September, or late March. It straddles the turn. For several weeks your current mornings are being compared against a stretch of a different season of you. The baseline is not wrong, exactly. It is just lagging, and during the lag your scores drift in one direction for a reason that has nothing to do with your health.
This is the same trap as what is your health score actually compared to, one step further in. It is not only a question of whether you are compared against yourself. It is which version of yourself, and when.
What to do about it
Four things, in order of how much they help.
Date the change before you explain it. If a decline started within a couple of weeks of a clock change or a real shift in weather, write that down before reaching for a cause. Season is a confounder, and treating it as one is the whole discipline. Two other guides already lean on this idea: how to tell if a supplement is working notes that when your sleep improved over eight weeks, so did the season.
Compare like with like. Last October against this October tells you far more than October against August. Year-over-year is the comparison that holds the season still.
Separate a night from a trend. A single elevated morning is usually last night, and why is my resting heart rate higher than usual covers what moves it. A four-week drift with no single bad night is a different shape of problem and calls for a different question.
Do not chase a score into a change you would not otherwise make. A seasonal drift that resolves by itself in spring is not a signal to act on. The cost of misreading it is doing something about nothing.
Where NUVARD fits
This is the kind of thing NUVARD is built to notice for you.
Rather than handing you a number and leaving you to work out whether the calendar explains it, NUVARD learns what your body actually does across a full year and gets more personal the longer it runs. An October morning gets judged against your October, not against an average that has not caught up yet. When something moves, you are told what moved with it, shown in your own data, so you can tell a season from a signal without doing the detective work yourself.
Every source you generate sits in one place: wearables, blood work, supplements, food, cycle. That is what makes a seasonal drift legible at all. One metric on its own cannot tell you the difference between autumn and a problem.
NUVARD is coming soon to iOS and Android. If you want it when it lands, join the waitlist.