It actually is often the case that changing the tense leads to more accurate translation. But a reliable Spanish Spanish teacher has told me futero is for forecasts, with voy + used more for plans. So in English, when we predict a change of season, it's future "will" not present, though "Spring is arriving soon" is heard, it's correct when signs of spring's imminent arrival have been observed.
It doesn't really matter. "La primavera" can become either "spring" or "the spring". Both make sense and have the same meaning. It's translating the other way (English to Spanish) that you have to be careful; while "la primavera" can turn into "spring" or "the spring", both of those have to turn into "la primavera." That is, even if you only wanted to say "Spring will come soon", you would still say "la primavera" (as I understand it).
I had the same doubts and found this http://www.englishclub.narod.ru/grammar/grammar_4_5.htm . It appears that it depends on the role of "summer" in a sentence.
"The spring arrives soon" is bad English, even Game of Thrones says "Winter is coming". Non native speakers need to know it is an error, that when made makes the speaker appear poorly educated. Correct usage : The spring of '77 arrived late. Now it is a specific season so definite article used.
A word of advice:
most of the rest of these six exercises is simply almost a repeat of the earlier extremely tedious ten Future ("going to do something") exercises completed a while back. you might therefore want to use copy and paste (cmd c and cmd v on a mac for example) on the words "going to" to save typing them countless times. life is short enough...