I live in southern California now, but I'm a New York City native. My best advice is to check a reliable online weather forecast - one of the best is http://www.weather.gov - and go from there. That's because NYC's weather can be highly variable from year to year. For example, normally there isn't snow till around Christmas time or early January. Not this year, however. NYC got snowed on in late October.
@ 5K: Ontario Mills 5K, Ontario, CA, 25:17
New Balance Palm Springs 5K, Palm Springs, CA, 24:32
@ 10K: LA Chinatown Firecracker 10K, Los Angeles, CA, 52:15