As for tropical storms/typhoons, the three worst during the war were on 13-14 Sep 1944 (E coast USA, 1 DD and several USCG ships lost, around 300 USN/USCG dead), 18 Dec 1944 (off Philippines, 3 US DD sunk, around 800 USN deads) and 3-4 Jun 1945 (again hit the Pacific Fleet, only some dead and no ship sunk but many damaged).
As for planes, weather losses were numerous during the war. The worst case for USAAF was as said before the 16 April 1944 (go on
www.aerothentic.co, you will find a list of all the losses this day somewhere on the site). RAF suffered too but in its case the worst losses were suffered when fog covered England when a heavy Bomber Command returns. In at least 2 occurences (from memory one in 1941 and one during the battle of Berlin, tens of bombers and more than 100 lives were lost due to fog in one night.
In at least 3 occurences, whole fighter formations were lost due to weather:
_ the 615 Sqn over Bengal Bay
_ on Sep 1942, one Eagle Sqn (US unit in RAF) get deported by strong winds and finished over Britanny rather than England. One had turned back early, all 11 other were shot down or crashed out of fuel.
_ on 21 Oct 1944, a 7 P-47 formation flying back to its New Guinea base found a tropical storm front between it and its base and all pilots ditched. In this case all were saved the next days (whole story at
http://www.pbyrescue.com/Stories/p47_story.htm).