anchor.diff:     + the lowest value of all reported `minAirTemperatureInCelsius` within that period (`PT12H`)
    + for max temperature in a certain time range, use the highest value from these two values:
      + the highest values of the hourly `airTemperatureInCelsius` values (`PT0S`)
  -   + the highest value of all reported `maxAirTemperatureInCelsius` within that period (`PT12H`).
  +   + the highest value of all reported `maxAirTemperatureInCelsius` within that period (`PT12H`)
  + + for max wind speed calculation `PT0S` period is used
  + + for max wind gusts speed calculation `PT1H` period is used
  + 
positive.code:             Content-Type: application/json
              x-amzn-RequestId: fbf51991-c2b2-11e6-bbb7-0153a49228b7
  
      + Body
  
             {
               "isoCountryCode": "UK",
               "observedUntil": "2017-01-13T10:35:31Z",
               "observedFrom": "2017-01-06T10:35:31Z",
               "minAirTemperatureInCelsius": -9.2,
               "minWeatherObservations": [
                 {
                   "meteoGroupStationId": "3065",
                   "meteoGroupStationName": "Cairngorm",
                   "observedAt": "2017-01-13T00:00:00Z"
                 },
                 {
                   "meteoGroupStationId": "3065",
                   "meteoGroupStationName": "Cairngorm",
                   "observedAt": "2017-01-13T06:00:00Z"
                 },
                 {
                   "meteoGroupStationId": "3065",
                   "meteoGroupStationName": "Cairngorm",
                   "observedAt": "2017-01-13T09:00:00Z"
                 }
               ],
               "maxAirTemperatureInCelsius": 14.1,
               "maxWeatherObservations": [
                 {
                   "meteoGroupStationId": "3313",
                   "meteoGroupStationName": "Rhyl",
                   "observedAt": "2017-01-11T09:00:00Z"
                 }
               ],
  			 "maxWindSpeedInKnots": 10.1,
  			 "maxWindSpeedObservations": [
                 {
                   "meteoGroupStationId": "43081",
                   "meteoGroupStationName": "Baskervilles",
                   "observedAt": "2017-01-13T00:00:00Z"
                 },
                 {
                   "meteoGroupStationId": "30651",
                   "meteoGroupStationName": "Leatherhead",
                   "observedAt": "2017-01-13T06:00:00Z"
                 }
  			 ],
               "maxWindGustInKnots": 53.06694,
               "maxWindGustObservations": [
                   {
                       "meteoGroupStationId": "3809",
                       "meteoGroupStationName": "Culdrose",
                       "observedAt": "2017-03-05T15:00:00Z"
                   }
               ],
               "maxSunshineDurationInMinutes": 720,
               "maxSunshineDurationObservations": [
                   {
                       "meteoGroupStationId": "3002",
                       "meteoGroupStationName": "Baltasound",
                       "observedAt": "2017-03-03T00:00:00Z"
                   }
               ]
             }
  
  Here `observedUntil` and `observedFrom` fields represent period that has been used to recalculate extreme values.
  Because extreme values for UK recalculate every hour, difference between `observedUntil` value and time of the request can be up to 1 hour.
  The fields `minWeatherObservations`, `maxWeatherObservations`, `maxWindSpeedObservations`, `maxWindGustObservations` and `maxSunshineDurationObservations` are arrays that contain all the observations when extreme value has been observed.
  
  The extreme values recalculating algorithm based on the following:
   + best observation parameters are used to calculate this
  
negative.code: 
  ## Retrieve extreme values [/extreme]
  
  By default [/extreme] endpoint finds extreme values for the last 7 days and for all UK's stations which are identified by wmoCountryId=91 in Geostation file (the id of UK). Extreme values recalculate every hour.
  
  ### Example
  
  `https://point-observation.weather.mg/extreme?isoCountryCode=UK`
  
  + Request extreme temperature data for UK for the last 7 days
  
      + Headers
  
  