question: How do weather forecasts calculate the "feels like X" temperature? How can a temperature feel like another temperature?
comment: Usually it's based off wind chill factors and humidity. They dont change the temperature, but they make it feel warmer or colder than the base temperature.
passages: Apparent temperature
  
  Apparent temperature is the temperature equivalent perceived by humans, caused by the combined effects of air temperature, relative humidity and wind speed. The measure is most commonly applied to the perceived outdoor temperature. However it also applies to indoor temperatures, especially saunas and when houses and workplaces are not sufficiently heated or cooled.
  
  BULLET::::- The heat index and humidex measure the effect of humidity on the perception of temperatures above . In humid conditions, the air feels much hotter because less perspiration evaporates from the skin.
   Section::::Influencing factors.:Relative humidity.:Interplay of temperature and humidity.
  
  Various types of apparent temperature have been developed to combine air temperature and air humidity. 
  
  For higher temperatures, there are quantitative scales, such as the heat index.
  
  For lower temperatures, a related interplay was identified only qualitatively:
  
  High humidity and low temperatures cause the air to feel chilly.
  
  Cold air with high relative humidity "feels" colder than dry air of the same temperature because high humidity in cold weather increases the conduction of heat from the body.
   The table below shows examples for three locations in the city of San Francisco, California. Note the corrected barometer readings are identical, and based on equivalent sea-level pressure. (Assume a temperature of 15 °C.)
   Many formulas exist for wind chill because, unlike temperature, wind chill has no universally agreed upon standard definition or measurement. All the formulas attempt to qualitatively predict the effect of wind on the temperature humans "perceive". Weather services in different countries use standards unique to their country or region; for example, the U.S. and Canadian weather services use a model accepted by the National Weather Service. That model has evolved over time.
   BULLET::::- "T" = air temperature, °C
  
  Section::::Alternative approaches.:North American and United Kingdom wind chill index.
   BULLET::::2. "Feels Like": Gypsy and Servo discuss actual temperature versus the wind chill factor. Servo then begins translating everything Gypsy says into "feels like..." statements, much to her annoyance.
  
  BULLET::::3. "Thanksgiving Clown": Servo dresses up as a clown, thinking it to be a Thanksgiving tradition. Crow consults an old World Book encyclopedia to verify.
   Section::::Temperature.
  
  Section::::Temperature.:Measuring conditions.
  
  The standard measuring conditions for temperature are in the air, above the ground, and shielded from direct sunlight intensity (hence the term, x degrees "in the shade"). The following lists include all officially confirmed claims measured by those methods.
   United States temperature extremes
  
  For the United States, the extremes are in Death Valley, California in 1913 and recorded in Prospect Creek, Alaska in 1971.
  
  The largest recorded temperature change in one place over a 24-hour period occurred on January 15, 1972 in Loma, Montana, when the temperature rose from . 
  
  The most dramatic temperature changes occur in North American climates susceptible to Chinook winds. For example, the largest 2-minute temperature change of occurred in Spearfish, South Dakota, a rise from .
  
  Section::::Lack of extremes.
   as possible problems with the reading have since been discovered. One of these was noted as early as 1949 by Dr. Arnold Court, who came to the conclusion that the temperature may have been the result of a sandstorm that occurred at the time. Court stated that "such a storm may have caused superheated surface materials to hit upon the temperature in the shelter." Weather historians such as Christopher C. Burt, and William Taylor Reid have also claimed that the 1913 Death Valley reading is "a myth", and is at least too high. If the 1913 record were to be decertified, the highest recorded air temperature on Earth would be , recorded both in Death Valley on June 20, 2013, and in Mitribah, Kuwait on July 21, 2016. 
   The heat index and its counterpart the humidex both take into account only two variables, shade temperature and atmospheric moisture (humidity), thus providing only a limited estimate of thermal comfort. Wind passing over wet or sweaty skin causes evaporation and a wind chill effect that the heat index does not measure. The other major factor is sunshine; standing in direct sunlight can add up to to the apparent heat compared to shade. There have been attempts to create a universal apparent temperature, such as the wet-bulb globe temperature, "relative outdoor temperature", "feels like", or the proprietary "RealFeel".
  
  Section::::Meteorological considerations.
   The apparent temperature (AT), invented in the late 1970s, was designed to measure thermal sensation in indoor conditions. It was extended in the early 1980s to include the effect of sun and wind. The AT index used here is based on a mathematical model of an adult, walking outdoors, in the shade (Steadman 1994). The AT is defined as; the temperature, at the reference humidity level, producing the same amount of discomfort as that experienced under the current ambient temperature and humidity.
  
  The formula is:
  
  where:
  
  BULLET::::- "T" = dry bulb temperature (°C)
  
  BULLET::::- "e" = water vapour pressure (hPa)
   AccuWeather created a unified and proprietary apparent temperature system known as "The AccuWeather Exclusive RealFeel Temperature" and has used the quantity in its forecasts and observations. The formula for calculating this value incorporates the effects of temperature, wind, humidity, sunshine intensity, cloudiness, precipitation, and elevation on the human body, similar to the rarely used (but public domain) wet-bulb globe temperature. AccuWeather has been granted a United States patent on The RealFeel Temperature, but the formula is a trade secret and has not been reviewed by other meteorological authorities. In response to AccuWeather's "RealFeel", The Weather Channel introduced their "FeelsLike" temperature reading.
   During summer, Cabo San Lucas is cooler than San José del Cabo by about 1.5 to 3 °C (3 to 5 °F). Sometimes during the summer, when winds blow from the Pacific Ocean instead of the Gulf of California, the differences in temperatures between San José del Cabo and Cabo San Lucas are higher.
   As the air temperature falls, the chilling effect of any wind that is present increases. For example, a wind will lower the apparent temperature by a wider margin at an air temperature of , than a wind of the same speed would if the air temperature were .
  
  The 2001 WCET is a steady state calculation (except for the time to frostbite estimates). There are significant time-dependent aspects to wind chill because cooling is most rapid at the start of any exposure, when the skin is still warm.
  
  Section::::Alternative approaches.:Australian apparent temperature.
   Section::::United States.:Texas.
  
  The temperature in Dallas, Texas on July 22 was . The temperature in Wichita Falls on July 19 and July 22 reached .
  
  Section::::United States.:Utah.
  
  The temperature in St. George, Utah on July 24 and 25 was ; on July 26 it reached .
  
  Section::::Mexico.
   In November 2001, Canada, the United States, and the United Kingdom implemented a new wind chill index developed by scientists and medical experts on the Joint Action Group for Temperature Indices (JAG/TI). It is determined by iterating a model of skin temperature under various wind speeds and temperatures using standard engineering correlations of wind speed and heat transfer rate. Heat transfer was calculated for a bare face in wind, facing the wind, while walking into it at . The model corrects the officially measured wind speed to the wind speed at face height, assuming the person is in an open field. The results of this model may be approximated, to within one degree, from the following formula:
   BULLET::::- "v" = wind speed (m/s) at an elevation of 10 m
  
  The vapour pressure can be calculated from the temperature and relative humidity using the equation:
  
  Where:
   The IPCC Fourth Assessment Report found that the instrumental temperature record for the past century included urban heat island effects but that these were primarily local, having a negligible influence on global temperature trends (less than 0.006 °C per decade over land and zero over the oceans).
  
  Uncertainties in the temperature record, e.g., the urban heat island effect, are discussed further in a later section.
  
  Section::::Warmest periods.
  
  Section::::Warmest periods.:Warmest years.
   BULLET::::- During June 2016, record heat appeared in Arizona, southern Nevada, and southern California. Burbank, California reached , Phoenix, Arizona reached , Yuma, Arizona reached and Tucson, Arizona reached , its warmest temperature in more than 20 years, on 19 June. Riverside, California reached , Palm Springs, California reached , Las Vegas, Nevada reached , Death Valley reached , Needles, California tied its all-time record high of while Blythe, California set a new all-time record high of on 20 June.
   The Australian formula includes the important factor of humidity and is somewhat more involved than the simpler North American model. The North American formula was designed to be applied at low temperatures (as low as ) when humidity levels are also low. The hot weather version of the AT (1984) is used by the National Weather Service in the United States. In the United States, this simple version of the AT is known as the heat index.
  
  Section::::External links.
  
  BULLET::::- National Center for Atmospheric Research Table of wind chill temperatures in Celsius and Fahrenheit
  
  BULLET::::- Wind chill calculator
   The standard wind chill formula for Environment Canada is:
  
  When the temperature is and the wind speed is , the wind chill index is −24. If the temperature remains at −20 °C and the wind speed increases to , the wind chill index falls to −33.
  
  The equivalent formula in US customary units is:
  
  Windchill temperature is defined only for temperatures at or below and wind speeds above .
   Section::::Alternative approaches.:Original model.
  
  Equivalent temperature was not universally used in North America until the 21st century. Until the 1970s, the coldest parts of Canada reported the original Wind Chill Index, a three or four digit number with units of kilocalories/hour per square metre. Each individual calibrated the scale of numbers personally, through experience. The chart also provided general guidance to comfort and hazard through threshold values of the index, such as 1400, which was the threshold for frostbite.
  
  The original formula for the index was:
  
  where:
  
  BULLET::::- "WCI" = wind chill index, kcal/m/h
  
  BULLET::::- "v" = wind velocity, m/s
   The variation in temperature that occurs from the highs of the day to the cool of nights is called diurnal temperature variation. Temperature ranges can also be based on periods of a month, or a year. 
  
  The size of ground-level atmospheric temperature ranges depends on several factors, such as:
  
  BULLET::::- The average temperature
  
  BULLET::::- The average humidity
  
  BULLET::::- The regime of winds (intensity, duration, variation, temperature, etc.)
  
  BULLET::::- The proximity to large bodies of water, such as the sea
   BULLET::::- In June 2017, more than 40 airline flights in the United States were grounded, with American Airlines reducing sales on certain flights to prevent the vehicles from being over the maximum weight permitted for safe takeoff and Las Vegas tying its record high at .
  
  BULLET::::- In June 2017 again, a heatwave in Iran broke record high temperature. On 28 June 2017, the city of Jask had a dew point of degrees, which is rare. But the highest temperature in Ahvaz soared to degrees and the humidity creates a heat index of .
   Average High °F (°C) while it should say °C (°F)
  
  Average Low °F (°C) while it should say °C (°F)
  
  Record Low °F (°C) while it should say °C (°F)
  
  Section::::History.
  
raw_presuppositions: The "feels like X" temperature is an actual temperature.
raw_corrections: The "feels like" temperature is merely how the base temperature feels, which can alter due to wind chill factors and humidity levels.