Heat-adjusted cross country pace Experimental
How to use
This is an experimental calculator for adjusting cross country (XC) race times for heat and humidity. To calculate a “heat-adjusted XC pace,” enter your race pace (in minutes per mile or minutes per kilometer), and the current temperature and humidity. The calculator will give you an estimate of what you can run in cool conditions.
You can also enter your cool-weather effort level, plus the temperature and humidity you’ll be racing in, and get an estimate of what you’ll run in the heat.
Tick the “show race times” checkbox to see input and output paces as a finish time for any cross country race distance, from 3200m to 10k.
If possible, enter the air temperature and the humidity, either as relative humidity (%) or dew point (the calculator works fine with either) as opposed to the heat index. Heat index is often less accurate for estimating the effects of hot weather race times, because heat index calculations are not designed for exercise and they blur the separate effects of heat and humidity.
This is an experimental calculator
I am still actively working on this calculator. I have validated its performance in collegiate and club runners, but I have not validated this calculator yet for high school and middle school runners. I am launching it now as an experimental calculator because it will be most useful for early-season and mid-season cross country races—a heat-adjusted calculator that comes out in December is not going to be useful for many of my readers!
Please use extra caution when using this calculator for middle school and high school athletes, and be sure to read the limitations section below so you understand the model’s assumptions and limitations.
Always use appropriate caution when training and competing in the heat, and follow your local athletics federation’s guidelines regarding practice and competition in hot conditions.
Pace mode versus effort mode
You can operate the calculator in two modes: pace mode and effort mode.
In pace mode (which is the default), you enter the pace you actually ran in the heat, and the calculator will give you an estimate of what you can run in cool conditions. For example, in pace mode you can read the calculator’s input and output as:
5:15/mi in 75° F and 60% humidity is the same effort as 5:08/mi in cool conditions.
In effort mode, which you can activate using the slider toggle , you enter your cool-weather effort level. For example, if you have run 5:15/mi in cool conditions, you can use the calculator as follows:
If you are in 5:15/mi shape in cool conditions, on a 75° F / 60% humidity day, you will run 5:22/mi in the heat.
Ideal weather for cross country is about 54° F / 12° C
When this calculator estimates the “ideal weather equivalent,” it’s using 54° F / 12° C (and about 65% humidity) as the ideal-weather comparator. This is the warmest temperature where there is no statistically detectable effect on race times. As a result, this calculator applies no adjustments for any weather conditions cooler than this threshold.
In the data I have seen so far, cross country performance is surprisingly stable even down to quite cold temperatures. I suspect part of the reason is that most of the data I have looked at has been for college and club runners, who I expect are relatively well-prepared (in terms of cold-weather racing gear). The situation may be different for younger runners who are less well-prepared.
How the calculator works
This calculator is a significant technical advance over my mainline heat-adjusted pace calculator. Unlike that calculator, it looks at how the same runner performs in hot weather and cool weather, during the same season. In contrast, my other calculator relies on similar finishing positions at large marathons (e.g. 100th place at the Chicago Marathon year-over-year), which carries along with it some possibly unfounded assumptions.
Notably, my heat-adjusted XC pace calculator accounts for things like the intrinsic difficulty of different courses, the baseline ability level of each runner, and changes in fitness throughout the season. This calculator estimates what the same runner at the same meet would have run, if the race was run in cool conditions.
The weather conditions used are the actual heat and humidity near the start time of the race, not daily averages or highs.
Limitations
Heat affects different runners to different extents. This app only provides an estimate of the typical effects of heat, for a typical runner.
This calculator assumes the effects of heat are the same (in terms of percentage slowdown) across all race distances. I have good statistical evidence to believe this is the case for 6k, and 8k, but the data are fairly weak outside that range (since 10k XC is almost always run in cool or cold conditions, and because I have not yet validated this calculator on high school and middle school performances, which have more results at 2mi, 4k, 3mi, and 5k).
A similar analysis found no material difference in the effects of heat on men versus women, which is why there is no sex setting in the app.
Remember that this app assumes “all else equal”—meaning wind, altitude, course conditions, etc. Often all is not equal!
Heat adaptation is particularly important for performance in the heat: the effects of heat can be much more severe for runners who have not trained in the heat in the last few weeks.
During the development of this app I tested whether I could detect any effects of heat adaptation on performance, but this analysis returned no significant results—probably because almost everyone who races in hot conditions is already adapted to the heat. Nevertheless, a non-heat-adapted runner is likely to handle heat worse than one who has been training in the heat.
Warnings about extrapolating beyond the data
The dataset I used to develop this calculator includes a wide range of temperatures and humidity levels, but certain combinations of heat and humidity are sparsely represented. Specifically, hot and dry conditions, as well as extreme heat of all kinds, are rare in the dataset—probably because sufficiently hot conditions mean a race gets cancelled or rescheduled. When the red alert pops up, you should be very cautious about trusting the results, since that means you are very far off the range of conditions the calculator was developed for.
Calculator settings
This calculator will remember your pace and its unit, whether race times are shown and for which distance, the pace-versus-effort switch, and your weather settings—input mode, temperature scale, and the temperature, humidity, dew point, and heat index values—in your browser’s local storage, so when you come back later you can pick up where you left off. You can reset everything to the defaults using the button. If you would rather the calculator did not remember your settings, switch off the Remember settings toggle.
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Contact
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