This year I (re)started my Camino in Astorga on 16th March.
For the first few days I walked in temps over 20C, and needed sunscreen. In fact I got a little burnt on the underside of my left arm. Sunglasses and sunhat.
Yet chilly at night, every night.
Then, after Villafranca the weather became cooler, and we climbed up as far as Laguna de Castilla and it was still sunny with clear and fabulous views.
We woke the next morning to 6 inches of snow! I'd brought gaiters and waterproof trousers but had mislaid my gloves - so spare socks were put to excellent use as emergency mittens! We were the first out, and climbed to O Cebreiro in virgin snow. It was clear for a while, and a joyous experience walking through beautiful snowy paths, but then the wind and snow got up again. We trudged onwards through deepening snow, our boots starting to leak, and beginning to feel miserable. At Fonfria, everything was closed. None of the albergues were open, and we knew the next one down the hill at Filloval was full (we'd called the night before) and the Casa Rurals in Biduedo weren't open. Eventually I knocked on the door of a house, handed over my phone and asked them to call me a taxi to Tricastela. It was a very expensive taxi at €30, but by then we didn't care, and we were glad to get safely into the warm and get dry again - best of all, the had a boot-drying cupboard beside the roaring log fire!
The next day I walked alone to Samos in snow then sleet, and the day after that the path to Sarria was somewhat soggy and muddy, but the air was clear and the day sunny.
So, expect all kinds of weather in March! Be prepared.
Here's the link to my March pics...
https://www.facebook.com/pg/juliawalksthecaminodesantiago/photos/?tab=album&album_id=680096255512858