Gathering clouds usually means rain or snow.

不断堆积的乌云意味着要降雨或者下雪。

youdao

The words have been spoken during rising tides of prosperity and the still waters of peace. Yet, every so often the oath is taken amidst gathering clouds and raging storms.

这些言词在繁荣潮起、在和平的风平浪静中说过，但很多时候，誓词是在阴霾密布中宣读。

youdao

The villagers were unaware of the beauty of the evening; they were used to it; they accepted everything, their poverty, their hunger, the dust, the squalor and the gathering clouds.

村民们没去注意傍晚的美，他们习以为常了，他们对眼前的一切默然承受——贫困、饥饿、尘土、脏乱以及天空聚集起来的云层。

youdao

Yet, every so often the oath is taken amidst gathering clouds and raging storms.

NPR: Obama Vows To Tackle Challenges

The OECD released strategic oil reserves in response to the situation in Libya to help bring down prices temporarily, but with the exception of a fall in WTI crude prices in the U.S., oil prices have remained steady despite the gathering clouds over the economy.

FORBES: Uneven Impact On Oil Stocks From OECD Trimming Oil Demand Forecasts

There are dark clouds gathering over 4G wireless carrier Clearwire.

FORBES: Clearwire: Merrill Now Sees Going Concern Risk; Target 50 Cents