3 sentences

1. 这些迹象是地震的预兆。

   zhè​xiē jì​xiàng shì dì​zhèn de yù​zhào.

   These signs are omens of an earthquake.

   Source: Dong Chinese Dictionary

2. 他毫无预兆地袭击了我们。

   tā háo​wú yù​zhào de xí​jī le wǒ​men.

   He attacked us without warning.

   Source: OpenSubtitles

3. 这种反常的天气预兆着风暴的来临。

   zhè zhǒng fǎn​cháng de tiān​qì yù​zhào zhe fēng​bào de lái​lín.

   This unusual weather portends the arrival of a storm.

   Source: Dong Chinese Dictionary