Personally, spring is one of my favourite times to be in Athens. During March and April, flowers will start blooming, and the smell of orange tree blossoms floats down pretty much every street. The temperatures from March to May average around 19 degrees, and towards the end of May it could get up to 25. For the outdoorsy traveller, spring is ideal in Athens. You can spend time hiking or biking around Mount Hymettus, or taking more local walks up Lycabettus Hill or around Philopappou, so make sure to bring your hiking shoes. And sunglasses are a must—even if the temperatures are cool, when the sun bounces off all that brilliant marble around Syntagma, you’re going to want a layer over your eyes.
It’s always tempting to dress for the weather you hope will happen, but don’t forget to pack layers. Nighttime will still get cool in Athens, so even though you can happily walk around in a t-shirt during the day, you’ll want to add a sweater at night. It’s also a good idea to bring layers if you plan on doing as the Greeks do and sitting at outdoor cafes and bars; as soon as winter ends and as long as it isn’t raining, you’ll find Greeks enjoying their coffees and cocktails al fresco.
And speaking of rain, while there isn’t as much of a chance of precipitation in spring as in the winter months, you will still want to pack for the possibility of rain showers. Another thing to think about: if you suffer from allergies, you may want to stock up on antihistamines or allergy medication before landing.