Remember the use of is or are depends on whether the noun is singular or plural. If the noun is singular you use is, Eg: There is one cloud in the sky. if the noun is plural you use are, Eg: There are many clouds in the sky.

There ARE a lot of clouds. :) Just remember “is” is singular. (I.e. “it is”, “he is”, “she is”) “Are” is plural. (I.e. “we are”, “they are”) Since there are “cloudS”, plural, “are” is the proper word. If you wanted to point out one particular cloud, for example one that had a certain shape, you could say, “look! There IS a cloud that looks like…”. I hope that helps.

There are a lot of clouds

LOT is a little confusing. Generally you should treat it as plural. Most other 'group' words are singular, however, A LOT OF is grammatically like MANY, which is plural. There IS a herd of cows BUT There ARE a lot of cows. There IS a crowd of people BUT There ARE a lot of people.

There ARE. As it’s plural