It has rained OR It has been raining

 Употребление Present Perfect Continuous в этом выражении подчеркивает длительность действия, в то времякак Present Perfect подчеркивает факт совершения действия: 

It is cold as it has been raining. 
It is cold as it has rained.

 
Чтобы лучше понять различия в смысловых оттенках этих двух выражений, можно переводить Perfect Continuous русским глаголом несовершенного вида. А просто Perfect – совершенного: 
Было холодно, поскольку (ночью) шел дождь. 
Было холодно, поскольку (ночью) прошел дождь. 

Вот несколько примеров использования Present Perfect с has rained и с has rained из различных оригинальных английских текстов, найденных в Сети при помощи Google: 

In the four months we've been in the Seattle area, it has rained six times. In fact, it has been sunny and on the upper side of 90 degrees more often than it has rained. And if it isn't 90, it's pretty darn close to it. 

California rains are different. Don't ride untill it has rained for 5 min. Since it rains so seldom the first rain mixes with (I'm told) oil and rubber on the road to make an icey covering. 

Teddy White came along my house this afternoon and gave me back my Rover book, and I gave him his Wizard book. It has rained hard today. 
Like yesterday it has rained hard all day. 

After it has rained hard and the heavens are roaring with thunder, do you tremble and call your Mama to hug you? 

It has rained hard all through that month — almost incessantly. And the narrow path that led from our house in that interior part of the city to the main street — the path where no vehicle or rickshaw could ply — has become a veritable river-in-spate. 

А вот несколько примеров на has been raining: 

I hoped that the rain would hold off until we got to the campground and had the tents set up. Well, no sooner than I had pounded the last tent peg into the ground, it began to rain (pour). It has been raining hard ever since (it's 2:30 PM now). 

I found Ajith Malli stopping every now and again, scratching his entire body. Clearly embarrassed, he offered that there were more leaches around these days on account of the rains. "We were lucky that the sun was out today. It has been raining hard every evening for the past several days". 

The river is flowing heavy for it has been raining hard and the river surrounds me.