What month is considered mid spring?

It depends on which hemisphere you live.

In the northern hemisphere spring starts on March 20/21 and September 22/23 in the Southern Hemisphere.

Some countries also designate a given date for the official start of spring.

No.

Spring starts around Feb 11th and ends April 30th with the solstice marking mid season. Summer starts 1st May and ends August 10th with the solstice again marking mid season. If people really think Spring starts on March 21st etc and mid Summer's day is 21st/22nd June when does Summer start? It cannot possibly start on mid summer's day can it? Starting halfway through is illogical.