In Collectanea is recorded the following:
“If the wind is in the east at noon on St. Benedict’s Day (March 21st), it will neither chop nor change till the end of May”
Another view stated that:
“As the wind is on St Benedict’s day. So it will stay for three months.”
Days in March were often seen as good indicators of the transition from the harshness of the winter into the calm of spring. It was also thought to be the day when time was created as noted by the Anglo Saxons:
“the earth shows by the shoots which are then quickened again that this is the time which should most rightly be the year’s beginning”
Ælfric was one who admired St Benedict and gave an opinion that St Benedict’s day in March ought to be the first day of the year because it was when the plants begun to grow. Clearly Farmers naturally too heed of the weather on St. Benedict’s Day and it was also said that:
“On Benedict sow thy peas or keep them in the rick.”
There is certainly a cold wind from the east across much of the UK until the 21st March in most years and so there appears to be some fact to the folk belief.