

今日は暖かいですね。
暖かい日に公園へ行きましょう。
沖縄は冬も暖かいですか。
"あたたかい(暖かい)" is in the lesson "Hot weather" (Level 15), along with 12 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.