Open Weather Mapの温度設定はデフォだとケルビンです。
これだとあまりに日常的でないので、変換してやる必要があります。
自前で変換してもいいですが……オプションつければ摂氏で取得できます
実際のところ
http://api.openweathermap.org/data/2.5/weather?id=1850147&units=metric&appid={{YOURAPIKEY}}
と、"units=metric"をつけてやればよいです。
{"coord":{"lon":139.69,"lat":35.69},"weather":[{"id":803,"main":"Clouds","description":"broken clouds","icon":"04n"}],"base":"stations","main":{"temp":6.29,"pressure":1017,"humidity":61,"temp_min":5,"temp_max":8},"visibility":10000,"wind":{"speed":4.1,"deg":140},"clouds":{"all":75},"dt":1519034400,"sys":{"type":1,"id":7619,"message":0.1444,"country":"JP","sunrise":1518989025,"sunset":1519028812},"id":1850147,"name":"Tokyo","cod":200}
と、tempのトコがちゃんと摂氏になっている事が確認できます
華氏の場合は"unit=imperial"。
……帝国単位系*1の意味ですかね。
大元のイギリスではもう使ってませんが、アメリカかジャマイカでは現役。
{"coord":{"lon":139.69,"lat":35.69},"weather":[{"id":802,"main":"Clouds","description":"scattered clouds","icon":"03n"}],"base":"stations","main":{"temp":43.3,"pressure":1018,"humidity":60,"temp_min":41,"temp_max":46.4},"visibility":16093,"wind":{"speed":3.36,"deg":180},"clouds":{"all":40},"dt":1519035120,"sys":{"type":1,"id":7622,"message":0.0111,"country":"JP","sunrise":1518989023,"sunset":1519028813},"id":1850147,"name":"Tokyo","cod":200}
*1:ポンド・ヤード法ともいうアレ