Very cool to see it in python! I only note that the AI agent added a daylight adjustment:
*Step 3: Daylight Adjustment for WBGT* - Daylight is defined locally as approximately 6:30 AM – 8:15 PM in summer for Sugar Land, TX. - Because it is daytime and the sun is contributing radiant heat, the following adjustment is applied: WBGT ≈ Tw + ((T − Tw) × 0.35) + 3.5 This accounts for the additional heat load from direct sunlight. *Result:* WBGT = 92.3 °F That added 7 degrees, which ain't nothing. Not sure if it is valid, but it gets it closer to how I feel outside. 95F at mid day here in the Gulf Coast doesn't feel like a comfy 85F, it feels way hotter. The other suggestion is to add the warning text. The whole reason I started looking at WBGT was because my sports trainer friend said that based on those categories, sports teams are mandated different things. Like maybe a cooler with ice and a tarp, so that if a player falls out because it is Extreme they are wrapped in an ice cocoon. Dave On Friday, June 26, 2026 at 11:44:29 AM UTC-5 [email protected] wrote: > I added this to the new-belchertown skin. > Straightforward. > Add user.wetbulb.WetBulbService to data_services line > Add wetbulb.py to your weewx-data/bin/user directory > Drop index_hook_after_charts.inc into /skins/new-belchertown > Restart weewx and then weectl reports run > > Look at the bottom of the page and you should see the status > > > > > On Tuesday, June 23, 2026 at 3:35:59 PM UTC-4 David Hathaway wrote: > >> Very interesting! I have been asking an AI agent to estimate the WBGT >> for me, and now I asked it what it was using. It uses the Stull formula >> and then a crude radiant heat adjustment. I think it is close enough for >> me to caution my wife to come in frequently so she doesn't perish. I'm >> frequently surprised that the WBGT is lower than our actual temperature and >> far below the "feel's like" that we are accustomed to. >> >> The agent says: >> >> *WBGT Calculation – Full Explanation* >> >> The process follows the weather-wbgt-safety skill, which uses local >> WeeWX data and standard approximations suitable for practical heat-stress >> assessment. >> >> *Step 1: Data Source* >> - The local RSS file at /www/rss.xml is read directly. >> - Current values extracted: >> – Outside Temperature (*T*): 95.4 °F >> – Outside Humidity (*RH*): 65 % >> – Wind: calm (not used in the WBGT formula here) >> – Timestamp: 13:40 CDT (used to determine daylight) >> >> *Step 2: Wet-Bulb Temperature (Tw)* >> Wet-bulb temperature is calculated using *Stull’s approximation* (a >> reliable, widely used empirical formula that avoids needing a full >> psychrometric chart). >> >> 1. Convert *T* from °F to °C. >> 2. Apply Stull’s formula (all temperatures in °C, RH in %): >> >> Tw = T × atan(0.151977 × √(RH + 8.313659)) + atan(T + RH) − atan(RH − >> 1.676331) + 0.00391838 × (RH¹·⁵) × atan(0.023101 × RH) − 4.686035 >> >> 3. Convert the resulting *Tw* back to °F. >> >> *Result:* Wet-bulb temperature = 85.3 °F >> >> *Step 3: Daylight Adjustment for WBGT* >> - Daylight is defined locally as approximately 6:30 AM – 8:15 PM in >> summer for Sugar Land, TX. >> - Because it is daytime and the sun is contributing radiant heat, the >> following adjustment is applied: >> >> WBGT ≈ Tw + ((T − Tw) × 0.35) + 3.5 >> >> This accounts for the additional heat load from direct sunlight. >> >> *Result:* WBGT = 92.3 °F >> >> *Step 4: Risk Classification* >> The value is compared against standard thresholds (in °F): >> >> - < 80 → Low >> - 80–85 → Moderate >> - 85–88 → High >> - 88–90 → Very High >> - > 90 → Extreme >> >> At 92.3 °F the conditions fall into the *Extreme* category, triggering >> the safety guidance. >> >> This method gives a practical, conservative estimate without requiring >> specialized instruments (black-globe thermometer, etc.). It is intended for >> personal decision-making rather than official occupational safety >> compliance. >> On Tuesday, June 23, 2026 at 2:19:25 PM UTC-5 Rainer Lang wrote: >> >>> the story is rather simple - it refers to how WGBT is determined and >>> what is supported by them. >>> The general formula for determining WBGT outdoors is: >>> WGBT = 0.7 x Tnwb + 0.2 x Tg + 0.1 x Ta >>> where nbw is natural wet bulb, g is BGT and a is outdoor temperature >>> - to get Ta in an Ecowitt context, you need an outdoor T&H sensor >>> (e.g. WH32) >>> - to get Tg in an Ecowitt context, you need a WN38 Black Globe >>> Temperature sensor >>> - to get Tnwb there is no sensor provided - therefore an approximation >>> method is being used >>> only in this combination Ecowitt provides WBGT data >>> and as WBGT has a medical dimension, the disclaimer is on there in their >>> (Ecowitt) web shop >>> >>> there are basically two approximation methods for determining Tnwb and T >>> g >>> 1. the so-called Stull formula which uses temperature, humidity and air >>> pressure (and derived entities like water saturation pressure) >>> 2. the so-called Lijlegren approximation which also uses wind speed and, >>> depending on the accuracy targeted, also sometimes solar radiation values >>> (direct, indirect, at different wave-lengths ...) >>> >>> 1. the Stull approximation implemented in the firmware now (and used by >>> many others) can lead to a deviation of up to 3° C >>> 2. is quite a sophisticated approach with several iterations, depending >>> on if the approach is used for Tnwb only or for Tnwb + Tg and if >>> solar values are included or not >>> >>> >>> to program the full Lijegren approach to reach a < 0.1% deviation from a >>> nbw-sensor, a coding of 300 - 400 lines of code is needed due to repetetive >>> iterations (so 'they' say) >>> - for so-called "medical" (health related) purposes, a simplified >>> Lijlegren approach can be used also using wind speed and it produces a >>> deviation of < 0.3° C - that's sufficient for the WGBT tiers/windows used >>> in different areas >>> - Ecowitt is considering to replace the Stull formula used now by a >>> simplified Llijlegren approach including wind speed to reach a higher >>> degree of accuracy >>> so, the accuracy of WBGT values provided by any piece of weather station >>> firmware or data logging software (like weewx) will depend on the approach >>> used. >>> >>> >>> On 23.06.2026 20:38, David Hathaway wrote: >>> >>> Thanks for the discussion pointer. I'll go snoop. >>> >>> On Tuesday, June 23, 2026 at 1:09:37 PM UTC-5 Vince Skahan wrote: >>> >>>> I recently saw mention of https://shop.ecowitt.com/products/wn38 >>>> which has a disclaimer that I didn't look into further. >>>> >>>> *"The WN38 Black Globe Thermometer measures and displays the black >>>> globe temperature only, which can be viewed on the LCD screen or through >>>> the Ecowitt or WS View Plus app.* >>>> >>>> *To display WBGT (Wet Bulb Globe Temperature) data in the app, the WN38 >>>> must be used together with an Ecowitt outdoor temperature and humidity >>>> sensor from either an outdoor array or a WN32(WN31 is not feasible)."* >>>> >>>> There is a lot of discussion at >>>> https://www.wxforum.net/index.php?topic=49316.0 which might be worth a >>>> read. Hope this helps. >>>> On Wednesday, June 10, 2026 at 10:03:28 AM UTC-7 David Hathaway wrote: >>>> >>>>> There is a 'wetbulp.py' (note the p) in this group that calculates it >>>>> as a xtype_service. This conversation, >>>>> >>>>> https://groups.google.com/g/weewx-user/c/FntQukhWY00/m/lM53yFt7AwAJ >>>>> >>>>> >>>>> On Wednesday, June 10, 2026 at 11:48:33 AM UTC-5 Vince Skahan wrote: >>>>> >>>>>> Quick search seems to say a WeatherFlow Tempest station has this, but >>>>>> I can't find it mentioned in any of their API so I don't see a way to >>>>>> get >>>>>> it into weewx for this one model station - >>>>>> https://community.tempest.earth/t/wet-bulb-globe-temperature/14386/11 >>>>>> >>>>>> Other threads and docs with the formula seem to say you need special >>>>>> sensors for this, so I can't speculate how WeatherFlow fakes something >>>>>> to >>>>>> generate that item. >>>>>> >>>>>> On Wednesday, June 10, 2026 at 8:36:45 AM UTC-7 David Hathaway wrote: >>>>>> >>>>>>> As the FIFA World Cup (tm) ramps up, we here in Houston are getting >>>>>>> a load of notices about how there is a mandatory water break in >>>>>>> matches, >>>>>>> even though it is played indoors. :-/ As I discussed this with my >>>>>>> friend >>>>>>> the sports trainer, he mentioned that Texas now has a rule that they >>>>>>> must >>>>>>> do certain things according to the WBGT. >>>>>>> >>>>>>> I have searched here for wet bulb additions to WeeWx. I see >>>>>>> discussions from 2024 and wonder if there is someone with a more recent >>>>>>> idea about implementing this. Does anyone calculate the Risk Level and >>>>>>> provide Guidance? >>>>>>> >>>>>>> I am trying out an agentic Ai to read the RSS XML feed; It loves >>>>>>> this format. I've not messed with the RSS export. Is there some >>>>>>> intrisic >>>>>>> gotcha? I really only care about current values. >>>>>>> >>>>>>> Dave >>>>>>> >>>>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "weewx-user" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To view this discussion visit >>> https://groups.google.com/d/msgid/weewx-user/29861e34-51f9-4df4-86e0-c9e06cdbdda0n%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/weewx-user/29861e34-51f9-4df4-86e0-c9e06cdbdda0n%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >>> -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/weewx-user/92c4880f-89ba-48af-b860-aee97ec2031cn%40googlegroups.com.
