The best time is after the ground has frozen but before the coldest weather arrives.

VOA: special.2009.06.30

And basically other interesting activities we did, weather studies, and time zone studies, which is part of the geography, and lots and lots of information.

还有其他一些有意思的活动，气候研究和时区研究，这是地理课上学的，还有很多很多其他信息。

麻省理工公开课 - 媒体、教育、市场课程节选

Their appearance changes endlessly with the light,the time of year, and the weather.

VOA: special.2009.10.07

The best time to plant the seeds is during cool weather.

VOA: special.2009.04.28

Furlong used the word "bizarre" to describe the weather on Cypress Mountain for this time of year, and added that safety comes first.

VOA: standard.2010.02.16

The runoff election between incumbent President Hamid Karzai and his main challenger, former foreign minister Abdullah Abdullah faces multiple challenges: Taliban intimidation, voter apathy and cynicism, increasingly harsh winter weather, and,most of all,a turnaround time of only two weeks.

VOA: standard.2009.10.28

"A little disappointed last night with the weather that got us, but we fought the weather last night, and it was just not the right time to launch yesterday, so we stood down, got into it today and it really rewarded everybody extremely well."

VOA: standard.2010.02.08