Does Your Resting Heart Rate Change With the Seasons?

Is your resting heart rate really different in July than it was in January, and should that worry you? Here is what large wearable datasets and small lab studies say about resting heart rate and the seasons, and a simple way to compare your own numbers fairly.

In this article

1. Does your resting heart rate change with the seasons?
2. Why would seasons change your heart rate?
3. What happens to HRV between summer and winter?
4. Could illness or hydration explain a drift?
5. How do you compare your numbers across seasons?
6. How should you handle hot weather and your numbers?
7. When should you see a doctor?
8. Frequently asked questions
9. Final thoughts
10. Sources and further reading

Does your resting heart rate change with the seasons?

Resting heart rate changes slightly with the seasons in large groups of people, usually higher in winter and lower in summer, but the shift is small compared with normal day to day swings. On its own, it is not a reason to worry.

Stress is another thing that moves these numbers, as covered in how stress affects your heart rate.

What the largest wearable study found

In 2020, Quer and colleagues published a PLOS ONE study of 92,457 US adults who wore a heart rate tracker on the wrist for at least 35 weeks.

The authors reported that resting heart rate peaked in the first week of January, then fell to a yearly minimum at the end of July. The seasonal swing was modest, on the order of a couple of beats per minute across the year.

What company data adds

Oura, a ring maker, has described its own 2016 to 2019 data in a company blog post: resting heart rate averages peaked in winter and were lowest at the end of summer. This is company data, not peer-reviewed research, and the post calls its patterns conversation starters.

Ultrahuman, another ring maker, ran a descriptive analysis of 4,703 members in 88 countries in 2024. Resting heart rate drifted down toward summer above the 50th parallel north and up near the equator, but the company says it ran no detailed statistics, so treat it as a hint only.

Why would seasons change your heart rate?

Seasons may change heart rate through several overlapping routes: outdoor temperature, how active you are, what you eat and drink, and how often you catch infections. No single cause has been shown to explain the winter to summer gap, and these factors tangle together in real life.

Temperature

A 2016 study in Scientific Reports by Madaniyazi and colleagues looked at 47,591 adults in Tangshan, China. It found a V-shaped relationship: heart rate rose by about 0.063 beats per minute for every 1 degree Celsius below 22 degrees, and by about 0.133 beats per minute for every 1 degree above 22 degrees. These are tiny per-degree changes, and the study covered one city, used fixed weather stations rather than personal exposure, and did not account for air pollution.

Activity, daylight and routine

Daily movement often changes with the seasons: long evening walks in summer, indoor routines in winter. Daylight is another proposed factor, but I found no trial in the sources I opened showing that it alters resting heart rate.

If your step count shifts with the weather, your baseline can move with it. See whether 10,000 steps a day is really necessary for how daily movement is usually framed.

What happens to HRV between summer and winter?

Seasonal HRV findings are mixed, and no one direction holds across every study. Results depend on who was studied and how much time they spent outdoors.

For background on the metric itself, see what HRV is and why it matters.

What the studies say

In 2000, Kristal-Boneh and colleagues recorded 24 hour HRV in 120 healthy men in both summer and winter and published the results in the Journal of Cardiovascular Risk. Average heart rate did not differ by season, yet HRV indexes did.

A 2016 paper in the International Journal of Occupational Medicine and Environmental Health compared 13 emergency ministry workers with 13 scientific workers in December and July. Seasonal HRV changes were not significant in the scientific workers, who spent more time indoors. The emergency workers showed lower parasympathetic and higher sympathetic parameters in winter than in summer.

Heat can also act directly. In a 2021 study by Abellan-Aynes and colleagues, 22 healthy adults were tested at 19 and 35 degrees Celsius, and heat exposure reduced HRV, mostly through reduced parasympathetic activity. It was a small sample.

Could illness or hydration explain a drift?

Yes, illness, dehydration and heat can all nudge resting heart rate up, which can look like a seasonal effect when it is really a short-term cause. Winter brings more infections, and summer brings sweating and fluid loss.

A 2020 study in Lancet Digital Health by Radin and colleagues used resting heart rate data from 47,249 Fitbit users to estimate flu-like illness, though the authors note that raised heart rate cannot be tied to infection alone.

Harvard Health notes that heat, humidity and haze can put stress on the cardiovascular system, and recommends drinking plenty of water.

Fluid and energy are covered in whether drinking more water boosts your energy.

How do you compare your numbers across seasons?

The fairest comparison is like with like: compare this January with last January, and this July with last July, using a 2 to 4 week average rather than a single day. Daily noise is as large as the seasonal gap, so averaging lets the signal show.

A rule of thumb for comparing like seasons

In the PLOS ONE study, a typical person's resting heart rate had a standard deviation of about 3 bpm from day to day. So a one day reading 3 bpm above usual is ordinary. A rule of thumb: treat a change as worth noticing only if your 2 week average moves clearly beyond that daily spread and stays there, and check the same weeks a year earlier.

This is a practical heuristic, not a clinical threshold.

My numbers across seasons

Fill in four rows a year, using a 2 week average each time.

How should you handle hot weather and your numbers?

In hot weather, expect a slightly higher resting heart rate and possibly a lower HRV, and treat heat symptoms, not the numbers, as the signal to act.

The NHS describes heatstroke as including a fast heartbeat, a very high temperature and hot skin without sweating, and says to call 999 if someone has these signs. Harvard Health adds that people on blood pressure medicines, particularly diuretics, should ask their doctor about dosing on hot days.

Some medicines change resting heart rate directly, so anyone on heart medicines, or who is pregnant, should ask a professional what is normal for them.

When should you see a doctor?

See a doctor if your heart rate feels racing, slow or irregular, if palpitations keep happening or are getting worse, or if a change comes with dizziness, chest pain or fainting.

The NHS advises seeing a GP if you have heart palpitations that keep happening or are getting worse. Seek emergency help for chest pain or severe breathlessness.

Frequently asked questions

Is a higher resting heart rate in winter normal?

For many people, a slightly higher winter reading is normal. A 2020 study of over 92,000 US adults found resting heart rate peaked in early January and was lowest in late July. The difference was only a few beats per minute, so look at trends rather than single days.

How many bpm can resting heart rate change by season?

In the large PLOS ONE study, the yearly seasonal swing was modest, about a couple of beats per minute on average. Around 20% of people had at least one week that moved 10 bpm or more, so a larger shift is not necessarily seasonal.

Is HRV lower in winter or summer?

Studies disagree. One study of healthy men found HRV differed by season, and a worker study found lower parasympathetic measures in winter only for outdoor workers. Small heat studies suggest HRV falls in hot conditions. There is no single answer, so compare your own like seasons.

Does hot weather raise resting heart rate?

It can, slightly. The 2016 Tangshan study found heart rate rose by about 0.133 beats per minute for each degree Celsius above 22 degrees, a very small effect per degree. Drink water and check how you feel, not just the number, and speak to a doctor if unsure.

Can daylight change my resting heart rate?

It has been proposed, but I found no solid trial evidence that daylight alone changes resting heart rate. Routine, activity and temperature change at the same time, which makes the effect hard to isolate, so treat any single explanation with caution.

When is a heart rate change a medical concern?

See a doctor if your pulse feels racing, slow or irregular, if palpitations keep happening or are getting worse, or if you feel dizzy or have chest pain. The NHS advises a GP visit for persistent palpitations. A sudden jump in your numbers alongside symptoms deserves prompt attention.

Final thoughts

Here is the short recap.

• Resting heart rate tends to be a few beats higher in winter and lower in summer across large groups.
• HRV findings across seasons are mixed, so compare your own numbers in like seasons rather than neighbouring weeks.
• Check illness, hydration and heat first when a number looks off, and see a doctor if you have symptoms or persistent palpitations.

Your turn: Have you noticed your own resting heart rate or HRV shifting between summer and winter? Tell us in the comments.

Sources and further reading

1. Quer G, Gouda P, Galarnyk M, Topol EJ, Steinhubl SR. Inter- and intraindividual variability in daily resting heart rate and its associations with age, sex, sleep, BMI, and time of year. PLOS ONE, 2020.
2. Madaniyazi L, Zhou Y, Li S, et al. Outdoor Temperature, Heart Rate and Blood Pressure in Chinese Adults: Effect Modification by Individual Characteristics. Scientific Reports, 2016.
3. Kristal-Boneh E, Froom P, Harari G, Malik M, Ribak J. Summer-winter differences in 24 h variability of heart rate. Journal of Cardiovascular Risk, 2000.
4. Markov A, Solonin I, Bojko E. Heart rate variability in workers of various professions in contrasting seasons of the year. International Journal of Occupational Medicine and Environmental Health, 2016.
5. Abellan-Aynes O, Manonelles P, Alacid F. Cardiac Parasympathetic Withdrawal and Sympathetic Activity: Effect of Heat Exposure on Heart Rate Variability. International Journal of Environmental Research and Public Health, 2021.
6. Radin JM, Wineinger NE, Topol EJ, Steinhubl SR. Harnessing wearable device data to improve state-level real-time surveillance of influenza-like illness in the USA. Lancet Digital Health, 2020.
7. Oura. Pandemic trends. Oura blog (company data, not peer reviewed), accessed 2026.
8. Ultrahuman. Impact of seasonal sunlight variation on sleep across latitudes. Ultrahuman Science (company data, not peer reviewed), accessed 2026.
9. NHS. Heat exhaustion and heatstroke. nhs.uk, accessed 2026.
10. NHS. Atrial fibrillation: diagnosis. nhs.uk, accessed 2026.
11. Harvard Health Publishing. Guard your heart during the dog days of summer. Harvard Health, accessed 2026.