Moved from Chicago to Austin two years ago. Pixel was in the passenger seat, both of us confused by the 105-degree welcome. Everyone warned me about the heat (they were right), the traffic (they were right), and the allergies (oh my god, cedar fever is real). Nobody warned me about my resting heart rate. I’ve been wearing a basic fitness tracker for years — nothing fancy, just a $60 refurbished Garmin Vivosmart that tracks RHR, steps, and sleep. When I pulled up my historical data last week to prepare for this post, I saw something strange that I’d never noticed before.

12 months pre-move (Chicago, all seasons): Average RHR 68 bpm (range 64-72) First 6 months in Austin: Average RHR 74 bpm (range 70-78) Months 6-12 in Austin: Average RHR 71 bpm (range 67-75) Now (year two, fully adapted): Average RHR 66 bpm (range 62-70)

That’s a 6-beat increase after moving, then a slow drop below baseline by month 18. What the hell happened? I dug into the physiology literature first. A 2019 study in *Temperature* (yes, that’s a real peer-reviewed journal — I was surprised too) exposed 20 healthy adults to 30°C (86°F) vs 23°C (73°F) for one week in a controlled environmental chamber. At the higher temperature, resting heart rate increased by an average of 8 bpm due to peripheral vasodilation — your heart works harder to pump blood to the skin for cooling. The effect was largest in the first 3 days and persisted throughout the week.

Austin’s average summer high is 35°C (95°F), and it stays above 30°C from May through September. My first summer here, I ran my AC at 74°F instead of Chicago’s 68°F to save money (electricity rates are higher here). That alone could explain the initial RHR jump. But why did RHR eventually drop below baseline? That took more data. I pulled my step counts from Garmin Connect and discovered something interesting: I walk way more in Austin than I did in Chicago.

Chicago winter: 4,200 steps/day average (it’s freezing, you hide inside)

Chicago summer: 7,800 steps/day (pleasant, but still car-centric)

Austin winter: 8,900 steps/day average (mild, sunny, actually want to be outside)

Austin summer (early morning or evening): 6,500 steps (too hot, but still more than Chicago winter)

The mild winters and year-round outdoor access — Zilker Park, Barton Springs Pool, the Boardwalk at Lady Bird Lake, the Southern Walnut Creek Trail — mean I’m moving more even when I’m not trying. That increased baseline activity, over time, drives cardiovascular adaptations that lower RHR. A 2021 meta-analysis in the *European Heart Journal* pooled 45 studies and found that every additional 2,000 steps per day (above a baseline of 5,000) was associated with a 1.2 bpm lower resting heart rate after 6 months, independent of other exercise. My step increase from Chicago winter (4,200) to Austin winter (8,900) is 4,700 steps, which predicts about a 2.8 bpm drop. Combined with the heat adaptation (which takes 6-12 months), that gets me from 68 to 66.

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Here’s the weird part — my calorie needs changed without my weight changing significantly. I tracked my intake for two weeks in Chicago (pre-move, using MyFitnessPal, same logging rigor) and two weeks in Austin (year two, same method). Same body weight (172 lbs at both times, measured on the same scale which I shipped with me). But maintenance calories went from 2,450 in Chicago to 2,650 in Austin. That’s an extra 200 calories per day — basically a Torchy’s taco or a scoop of Amy’s ice cream or a couple of craft beers at Zilker Brewing.

Where does that 200-calorie increase come from? Two sources. First, the increased baseline activity (steps) accounts for about 80-100 calories per day, based on standard metabolic equations (0.04 calories per step times 4,700 extra steps = 188 calories, but that’s walking, which is efficient, so maybe half that — call it 90). Second, the thermic effect of living in a hot climate. Your body burns calories to cool itself — sweating, increasing cardiac output, maintaining thermal homeostasis. A 2020 study in *The Journal of Clinical Endocrinology & Metabolism* put people in a 35°C room for 60 minutes and measured metabolic rate via indirect calorimetry. It increased by 12% compared to 23°C, purely from thermoregulatory costs. Over a full day, that could add 150-200 calories. So my 200-calorie bump is plausible.

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What does this mean for your tracking if you’re moving to Austin — or any hot, walkable city? Don’t panic if your RHR jumps in the first summer. Give it six months. Your cardiovascular system adapts through increased plasma volume (blood volume expands to help with cooling, which initially raises RHR but then normalizes) and improved heat dissipation. A 2024 paper in *Medicine & Science in Sports & Exercise* followed 45 people who relocated from cool climates (average annual temp 12°C) to hot climates (average 26°C). Their RHR increased 6-10 bpm in month one, then returned to baseline by month four. By month 12, 60% of participants had RHR *lower* than pre-move because of increased incidental activity (they walked more in their new environment).

Also, adjust your calorie expectations. If you’re from a colder place and you move to Austin, you might need to eat more to maintain your weight — or you might lose weight without trying. I gained 3 lbs in my first year (not a lot), but that was because I was eating like I was still in Chicago and not accounting for the activity bump. The calorie needs calculator on my site has a “climate adjustment” toggle now. It’s crude (just adds 5-10% for hot climates), but better than nothing.

The takeaway from my two years of RHR data isn’t “move to Austin.” It’s that your body’s data will lie to you if you don’t account for context. A high BMI reading during a heat wave? Could be water retention from sweating (your body holds onto fluid to help with cooling). A high RHR your first month in a new city? Could be your cardiovascular system working overtime to adapt. A sudden drop in calorie needs in winter? That’s real — seasonal differences in non-exercise activity thermogenesis (NEAT) are documented in a 2023 *Obesity* paper. Always ask: what’s the confounding variable here?

I’ve got the full 24-month RHR graph pinned on my fridge. It looks like a roller coaster that starts high, dips, goes up again during last summer’s heat wave (July 2025 — remember that one? 108°F for four days), and ends slightly lower than it started. If you’re tracking your own RHR and see weird seasonal swings, ping me through the contact form on bmitool.org. I’ll send you the spreadsheet template that separates weather effects from fitness effects. It’s got conditional formatting and a “moving average” column. Because of course it does.

— Jamie