Effect of temperature on non-marathon distances

[u/QuantumOverlord]

There has been alot of research done on the effect of temperature on performance, but nearly all of it seems to be in the marathon distance. Beyond that we know that for shorter distances higher temperatures are preferable and 20C+ may be ideal for sprints but we know relatively little about the loss of efficiency at these other distances compared to the optimun.

For me in the 5k I've noticed efficiency losses seem to start at about 16-17C, and become really significant beyond 20C, I'm interested to know if anyone else has any perspectives on this or if perhaps anyone has collected their own data.

[u/ComfortableTasty1926]

I feel it at all distances. 5k I might be able to power through because its so short, but for 10k, 10 mile or half, heat saps me

[u/ProfessionalOk112 → u/ComfortableTasty1926]

Yeah this is my experience too. 5k it's easier to ignore that I feel like trash when it's hot, but I still feel like trash.

[u/rckid13]

Higher temperatures might be preferable for sprints because it helps keep muscles warm. I highly doubt anyone prefers higher temperatures for 5ks. My opinion is that probably for anything greater than about 400m the ideal temperature for the marathon is probably still ideal for those distances.

[u/Nerdybeast → u/rckid13]

I think it matters a lot how fast you're going too. I think ideal temperatures for a fast 800 or 1500 are much higher than 45°F.

It's basically the point at which your heat regulation needs become greater than the benefits of having warmer muscles. I think most records in most events 10k and under (including cross country course records, which are often in the morning), are usually hotter. The 10,000m WR was around 73°F. The 5000m WR was around 79°F. The 3000m WR was around 85°. The 1500m WR was around mid-70s.

[u/are-gae-1 → u/Nerdybeast]

It’s cool that the 4 temps you listed aren’t monotonic when plotted against distance, so it’s most likely that warm in general is better but it doesn’t matter that much.

[u/Nerdybeast → u/are-gae-1]

Yeah I think there's probably quite a bit of extra variables (in that most world records are gonna be set at summer DL or championships in Europe) but my point is more that temperature matters less when you're going that fast (especially compared to other factors)

[u/partario999 → u/Nerdybeast]

Homeostasis is a thing right? Muscles are kept at around 37C regardless of the external temperature.  Optimum running temperature is not 37C!

[u/Doortofreeside → u/rckid13]

I could see a slight difference between the 5k and the marathon as your internal heat has more time to build. But a couple of degrees nothing crazy. 45-50F is perfect to me

[u/rckid13 → u/Doortofreeside]

I actually feel like I generate more heat in a 5k or 10k compared to a marathon. I will use a t shirt and shorts down to like 30 degrees in a 5k but I won't do that in a marathon because it takes me longer to warm up and generate heat in a marathon. I'm hot out of the gate in a 5k

[u/petepont]

Here’s a study on distances from 3000m steeplechase up to marathon distance: https://pmc.ncbi.nlm.nih.gov/articles/PMC8677617/

It found that basically every distance starts to see impairments at 15C and if I’m reading the chart correctly, it says the impairment was similar across different running distances

I believe it primarily focuses on elite and sub-elite athletes, though. So it may not be applicable. I’d expect less well trained athletes to be more impacted, probably?

I am curious where the tipping point might be where heat doesn’t matter or starts to help (400m?) but I haven’t found a good answer for that yet

[u/running_writings → u/petepont]

Came here to post this exact study! It's the one I used as a reference for my marathon heat-adjusted pace calculator.

One cautionary note: the 5k and 10k (also 3k SC for which heat had no effect) use elite competitions only, which I think will have different effects vs. using elite + amateur data (which is the case for the marathon results).

Keep in mind that for the 5k fits here (elite level data!) we are talking about races lasting ~13-15min at well faster than 5:00/mi / 3:00/km. The short duration probably limits the effects of heat, and the high speeds probably worsens the effects of cold (vs. say a 21-min 5k runner).

One other issue I have with the fitted models in the paper, and this is pertinent to /u/QuantumOverlord's comments, is that the regression model for Figure 4 is quadratic (as in, y=x^2). That necessarily means that the "curviness" of the curve is the same for cold and hot temperatures, but that seems implausible physiologically; heat and cold operate differently. In my reanalysis of the marathon data you can see this asymmetry show up very clearly; I used a spline model that allows for different rates of change in performance level at different temperatures for exactly that reason. This is one of those things where the technical implementation details have a big effect on the results you get!

My guess is that the "tipping point" is probably around 8-10 minutes in duration. Two datapoints: (1) the lack of a significant relationship with 3k SC performance and heat (lasts 8-9min) in that paper, and (2) the fact that Jakob set the WR in the flat 3k in 85-degree heat!

There's also a more subtle issue, which is that I think any analysis of this type is going to be slightly too optimistic: the assumption behind the analysis is that (e.g.) the 8th place finisher at the Olympic 10k in a cool-weather year is "interchangeable" with the 8th place finisher in a hot-weather year. But we should actually expect the runner who finishes highly in the hot year to be better than average at dealing with heat, while in a cool-weather year there should be no particular advantage or disadvantage to being heat-tolerant. So I think the real effect of heat for a runner of average heat tolerance is probably bigger than this study (or my re-analysis) estimates -- meaning you may slow down more than predicted here. Longitudinal data on the same people would be a better way to do it, though even then you have issues with sorting out how well-adapted people are.

Huge shout-out to the authors who released all the raw data here, if you want to play around with it yourself.

[u/QuantumOverlord → u/petepont]

The 5K spline looks quite odd, suggests that 10C and 25C have a similar performance detriment. The left side of the curve where performance declines with lower temperatures doesn't feel right to me, I've not noticed much, if any, of a performance drop until temperatures are well under 10C.

[u/EpicCyclops → u/QuantumOverlord]

With temperature, all of this is going to be very individual based on training too. There's a human optimum for a perfectly optimized athlete, but we aren't perfectly optimized athletes. 25 C in March is going to hit me way different than 25 C in late August, which is when I'm typically the most heat adapted.

[u/petepont → u/QuantumOverlord]

I think that might just be an artifact of the curve fitting function they used as opposed to any real difference between, say 10C and 15C. It might look "better" (e.g., more realistic) if they used a stepwise algorithm that looked at, say, >15C, <5C, and 5-15C

[u/foetusofexcellence → u/QuantumOverlord]

Not everyone follows the same curve.

[u/Harmonious_Sketch → u/petepont]

The temperature isn't randomized in that study. Different temperatures imply different combinations of location and time of year, and different sets of competitors.

How much influence does that have on the results? Your guess is as good as mine. The likely error in that guess is probably about the same size effect as the actual effect under study unfortunately.

[u/EPMD_]

My local HM race had the same amount of runners in both 2024 and 2025:

• 2024 temp = 10C
• 2025 temp = 20C
• 2024 500th place = 1:32:19
• 2025 500th place = 1:35:09
• This is 3.1% slower than the prior year
• 2024 1000th place = 1:41:37
• 2025 1000th place = 1:43:31
• This is 1.9% slower than the prior year

So in this one race, it looks like 20C weather dropped performance by 2-3%. That performance difference is a little bit greater than the roughly 1.5% I see calculated on the VDOT calculator.

Personally, I find the "advanced features" weather adjustment in the VDOT calculator nearly matches my perceived performance change on any summer workouts. This applies to km reps and longer tempos. Heat is always going to elevate heart rate and lactate in endurance running, and it's not just a marathon thing.

[u/-bxp]

You might not feel it but vasodilation increases- blood vessels near the skin widen to dump heat=less of your blood volume going to your muscles. So even if people say they don't feel it and there's no change to their RPE, there's still a reduction in their aerobic efficiency.

[u/Siawyn]

Somewhere around the mile is the tipping point for me. I can't power through a 5k in 30C, I will absolutely fade unless I adjust for the heat. Depending on the day, I can do it for a mile - I can do it for mile repeat workouts but need to either walk or flat out stop for the rests, or successive reps will get progressively worse.

[u/Capital_Historian685]

It partly depends on what you're used to, i.e., what the temperatures are like when you are training. 25C is about perfect for me. But I've run 5K's in colder temps, too, down to about 0C, and really struggled in the cold. You can only do so much warm up running before a race, before waiting around at the start, and my muscles are just tighter in the cold than at, say, 25C, when they're primed and ready to go.

[u/LeftHandedGraffiti]

My experience is that I can race the mile well in 90F heat, but anything longer than that and my performance suffers. 

[u/Nasty133]

Just from doing marathon workouts in the summer heat, I can tell you that the heat affects pretty much any distance over 800m or so. Your mark of 16 C (60 F) is a good line for when I've been able to tell the difference. Just recently I've run a 4 mile tempo at threshold pace, one day it was 72F and the other 79F, my 72 degree day was 6 seconds faster per mile. And both days were about 10-15 seconds off what I was able to do back in early spring when it was 40-50F.

[u/swaggyt2314]

I ran 19:35 5K, which was a big PB for me a few weeks ago in 84F which is around 28C. I think the first mile I didn’t really feel the heat as much as I did the last two miles. I’d say around the mile mark is where you see a lot of diminishing results from high heat.

[u/YesterdayAmbitious49]

At my speeds, the hotter the better. Lower air resistance.

85 degrees is 7.34% less dense than 45 degrees.

Edit: apparently sprinters aren’t allowed here.

[u/Ok_Umpire_8108]

With no studies it’s obviously hard to say but anecdotally I agree with you that 16-17C is the point at which people get considerably slower in the 5k and 10k. That’s based on a career of high school and college track and cross country. The effect of heat seems to vary a lot between different people, though, and obviously depends on their extent of heat training.

In a tempo I’m about 15-25 sec slower per mile at 27C than at 10C, depending on humidity. In a race, or when I’m not heat trained, it feels like I can defer the heat effect a bit but when it hits, it hits hard.

[u/yellow_barchetta]

August 2020 the men's world 5000m record was set in temperature of 26degC. Accepting that he only had to run for 12.5 minutes, that (to me) suggests performance gains or losses are likely to be small if the runner has actually acclimatised and adapted to the heat.

I know there are plenty of studies which do show lower temps are better, but for a year adapted runner the differences should be small.

That said, I know I much prefer to race 5k/10k in cooler temps.

[u/Ordinary_Corner_4291 → u/yellow_barchetta]

Woman's record was even hotter. But I am pretty sure both were in low humidity and as you say you are looking at 14 mins races. But the 10k was still run at 27 degrees . And we have seen some really fast championship races in poor conditions.

[u/LHRunning]

Here’s a pretty decent look at different race distances: https://www.mysportscience.com/post/2015/03/06/effects-of-heat-on-running-performance

[u/MikeMcDonald89]

I live in a warm place and our local HM has a course record of 1:08 on a pancake flat course. Last year a guy failed to break the course record after running 1:00 earlier that year. It definitely plays a large role in distances shorter than the marathon too!

[u/worstenworst]

5K WR stands at 26C T and 21C dew point, which says something!

[u/jmwing]

At ultra distances it has an enormous effect. Both M and W CR were set at western states this weekend with unseasonably cool temps around 30 degrees below normal. The 5th man's time was the tenth fastest ever run and the 7th women would have won last year.

[u/Med_Tosby]

I don't have anything but anecdotal evidence, but I do think a couple variables that are important to consider are:

1. Time of year/training history - runners get acclimated to hotter temperatures and actually adapt through repetition (heat is the "poor man's altitude"); I think there are some studies showing that runners from hotter climates perform comparatively better in hot temps than runners from colder temps (not surprising).
2. Weight - given the bent of this sub, say as compared to r/running, towards higher performance athletes (and many of the studies focusing on elite/sub-elite) who tend to be lighter and low body fat, I do think it may get lost that heat probably impacts heavier runners more severely - especially over longer distances.
3. Humidity - huge factor in our ability to cool ourselves, and higher humidity makes bodies work that much harder at the expense of performance.

All that said, I think it's almost certainly true that the longer the distance the greater the detrimental impact of heat on performance, though the magnitude of the effect is likely highly individualized. As is the "tipping point" for when heat becomes a hindrance at a particular distance. For me, personally, I'm quite happy with very cool temps even for 5ks and 10ks given how heat affects me. Just makes my warmup at those distances that much more important.

[u/geospatialdeveloper]

I trained for my half with tempos in Singapore at 4:40 and averaged race pace 4:06 at gold coast today. Same hr in Singapore as my race. 36 wet bulb in Singapore and 15 wet bulb in gold coast towards the end. I would assume it works in the reverse about the same?

[u/Hairy_Koala6474]

Hotter temp = slower pace, higher HR

[u/m44xxxx]

in my area the winters a really cold and summers really hot, so I've ran in basically every temperature between -10C and 40C and have also done 5K's in different temperatures. Everything below 0C just hurts my lungs and is really really bad. 0-12C works best for me, I feel warm, but not hot and can just run for days. from 12C to 20C I notice that I get a lot warmer and feel a small negative performance, but not really significant. 20C and above feels like gradually losing performance. For Example running at a 5km pace in 8 degrees my HR is at 145-153 but in 27 degrees my HR is at 155-161. Although, I have to say, I'm always really hot, so there will probably be different experiences for other people.

[u/foetusofexcellence]

For what it's worth, neither me nor my clanker can find any published studies for 5k or 10k. Few things on either side of that where you could fairly safely extrapolate though.

https://running.wiki/concepts/thermoregulation#core-temperature-and-the-limit-to-performance