DETERIORATING WX PROMPTS A PRIVATE PLT TO LAND AND RE FILE FOR A DIFFERENT RTE. CONTINUED DETERIORATION OF THE WX ON THE NEW RTE PROMPTS A TURN BACK FOLLOWED BY INADVERTENT ENTRY INTO CLASS D WITHOUT CLRNC.

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I ENTERED ZZZ'S CLASS D AIRSPACE NE NEAR ZZZ1 ARPT AND REMAINED IN SAID AIRSPACE UNTIL ZZZ TWR CLRED ME TO LAND. I WAS ADVISED TO CONTACT THE TWR FOR POSSIBLE AIRSPACE CONFLICT. I CONTACTED THE TWR BY PHONE AND WAS MADE AWARE OF MY MISTAKE. WHY (CHAIN OF EVENTS): XA:30 AM; FILED FLT PLAN; DEPARTED ZZZ2 WITH INTENTION OF FLYING OVER MOUNTAINS TO ZZZ3. DETERIORATING METEOROLOGICAL CONDITIONS FORCED ME TO CHANGE FLT PLAN. LANDED AT ZZZ4 AND CLOSED FLT PLAN. PHONED IN NEW FLT PLAN; ZZZ4 TO ZZZ1 AND ON UP TO ZZZ3. AFTER DEPARTING ZZZ4; I ESTABLISHED FLT FOLLOWING WITH APCH. WX WAS DETERIORATING; SO THEY PUT ME BACK ON 1200 AND VFR. I WAS FORCED LOWER AND LOWER BY CLOUDS AND HAD TO CHANGE COURSE DUE TO RAIN. THIS PLUS MY FAILURE TO RECOGNIZE ZZZ AS CLASS D WHILE IN FLT CAUSED MY INADVERTENT AIRSPACE VIOLATION. I ONLY DISCOVERED THE PROB WHEN ZZZ INFORMED ME. I PLAN TO REVIEW MY AIRSPACE INFO WITH CFI; TAKE MORE TIME IN FLT PLANNING FOR CONTINGENCIES. BE MORE VIGILANT WHEN READING CHARTS IN FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS ABLE TO MAINTAIN VISUAL CONDITIONS THROUGHOUT THE INCIDENT. ONCE HE REALIZED HE WAS NEAR ZZZ; HE FOUND THE APPROPRIATE FREQ. THE TWR WAS ALREADY TRYING TO CONTACT HIM.