I am looking for a meteorological measure (formula) of something which combines 2 or more of the following:

temperature, humidity, cloud, wind, precipitation, UV

I have searched, and for example, found the heat-index which combines temperature and humidity, but unfortunately the heat index only has a meaning when the temperature is high, I would be needing a measure which would always "make sense".

(Background information: I want to set up a mathematical model where some climate information is also included as a side measure and therefore want to "merge" the available time series to a new measure and have more information as input, since otherwise I could always only include a single information.

Further background information: Would like to measure the effect of those variables (single variables, or better yet, combination of some of those) on the time-varying infection rates of COVID infections, the reason those were chosen is because in papers surrounding the topic "meterological factors" and "Covid infections" those were chosen most often)

  • $\begingroup$ Your question is posed in an odd way, more like you're interested for some requirement rather than out of interest to make something useful. But if you're just looking for a more encompassing apparent temperature, questions like How to Calculate Temperature Humidity Wind Index may be of use. $\endgroup$ Commented Dec 19, 2021 at 22:19
  • $\begingroup$ @JeopardyTempest Thank you for the link, but I do not really get your point where you said that my question is posed oddly because I'm looking for some requirement? Because as a mathematician I do not have enough background to come up with something useful myself from the available data, and as stated the climate information is only a side measure in my model, and therefore wanted to ask if there are already formulas which combine these information in some way and I could also not do this and only include each of the measures as a stand-alone but just wanted to see if there other possibilities $\endgroup$
    – maths
    Commented Dec 19, 2021 at 22:46
  • $\begingroup$ The wording was just a bit odd... (the way you asked for "2 or more of the following" rather than talking about the reasons you choose those, and also talked about how that'd just be more input, rather than how it'd make something better)... but maybe it's a language issue or me being a fool and reading things differently than most, either way, no ill will intentions, and do hope you find what you need :-) $\endgroup$ Commented Dec 19, 2021 at 22:59
  • $\begingroup$ @JeopardyTempest: The THW is exactly something I was looking for, but is there a paper/link where "THW = HI - (1.072 * W)" is derived in some way? Because I could not find this formula anywhere on the internet. and would this be an index which would make sense for all temperatures/humidities/wind speeds? (again, I'm a mathematician and have really low meterological background knowledge) Because I have read that HI only makes sense for warmer temperatures and would like to know if it is the same for THW $\endgroup$
    – maths
    Commented Dec 19, 2021 at 22:59
  • $\begingroup$ @JeopardyTempest. That's because the model I'm setting up is really open ;) so I have no strict requirement what to do the with the meterological data available, I have added further background information, hope my question and intentions are clearer now. $\endgroup$
    – maths
    Commented Dec 19, 2021 at 23:14

1 Answer 1


The wet bulb globe temperature (WBGT) combines 4 or 5 of your variables, while the wet bulb temperature (Tw, or equivalently the heat index, HI) combines only temperature and humidity. This chart from the National Weather Service compares what goes into these measures:

WBGT vs heat index comparison

Based on your further background information, it could be worth running the model for both WBGT and Tw, and see which works better.

For COVID infection rates, I suspect that the comfort level of outdoor dining is important. That may be captured best by Tw (or HI), because it neglects wind and sunlight. In a dining situation, people can deal with these factors by modifying their immediate surroundings (with shade, lamps, fans, or screens), so neglecting wind and sunlight may be appropriate.

WBGT is touted as a better indicator of outdoor safety for more intense exercise or labor, but in those cases, people may not be within 6 feet of each other for long continuous intervals. So WBGT may be a better predictor of activities that don't affect COVID infection rates as much.


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