Weather: Cold, wet, damp, probable snow or mixed frozen precipitation. Temps can range from 10-40 degrees Fahrenheit, but it's usually between 25-35. With a wind chill, it can get below zero. When the white stuff hits, wait until it ends and break out a good set of boots.
What to Wear: Dress in layers because stores and restaurants will likely keep things warm. Bring an umbrella, warm coat, scarf, hat, gloves, and some good weather resistant shoes. Watch out for big puddles in subway station entrances.
Cost: The cheapest time of year to go because of the weather. Flights cost less and hotel prices drop on Jan 2. Here's a hint - try the TKTS booth at the South Street Seaport or in Brooklyn instead of the Times Square booth for shorter lines. And of course the first week or two of January usually means post-holiday sales.
Seasonal things to do:: Ice skate in Bryant Park (free) or Central Park. Feast on comfort foods (brunch!) in the West Village. Shop all the post-holiday clearance sales. Get to a Knicks basketball game or try a New York Rangers hockey game. Restaurant Week falls at the end of the month, but be prepared to make reservations well ahead of time. Lunar New Year in Chinatown is also an experience. Stay indoors & hit the museums. Attend the Westminster Kennel Club Dog Show at Madison Square Garden. Get married on the observatory at the Empire State Building on Valentine's Day.
Weather: March is not as frigid as February, but you'll still need a warm coat. March temps can range from 30-50 degrees Fahrenheit, and you're more likely to see 40's as a high. April is more likely to be in the 45-65 range; consider yourself blessed if it gets beyond 70, which can and does happen, but usually means a thunderstorm following. An April "heatwave" is one of the best times to be in NYC.
What to Wear: Bring an umbrella, warm coat, and maybe gloves. It probably won't snow, but it has been known to snow in April every few years. Still watch out for big puddles in subway station entrances. Wellies are a plus in avoiding puddles that collect at street corners; you can plow right through them without getting your feet and pants drenched.
Cost: Flights & hotel prices certainly go up as the weather improves, but this is still off-peak to shoulder season. Winter clearance sales happen as spring clothing hits the racks. You still have better than average odds at getting same day half price Broadway show tickets at TKTS booths.
Seasonal things to do:Ice skating in Central Park if it's still cold enough, otherwise, get out to Central Park and stroll around for great people watching. Bear in mind that spring flowers arrive by the end of April, so investigating the leafier gardens is worth it. It's generally packed on the first warm weekend (50 degrees). Attend the St. Patrick's Day Parade on March 17 along with hundreds of thousands of NYers who become Irish & call in sick that day. Catch a New York Mets or New York Yankees home game in April. Go to the New York International Auto Show at the Jacob Javits Convention Center. The Tribeca Film Festival begins at the end of the April, but book ahead.
The circus - Ringling Bros. and Barnum & Bailey - comes to town in early April; each year the news covers the grand entrance of elephants walking through the Midtown Tunnel. In Brooklyn, see NY's version of a sakura (cherry blossom) festival at the Brooklyn Botanic Gardens near Prospect Park. See the parade of Easter bonnets and spring dresses up Fifth Avenue.
Weather: Spring in New York City is the best time to be in the city, without doubt. Spring usually means less humidity and temps between 50-80 degrees, though June occasionally sees a 90 degree day. An occasional humidity soaked heat wave can strike, but it usually feels nice the first time around. Spring is all about eating al fresco and enjoying the low humidity.
What to Wear: Bring an umbrella (always bring one - it's a walking city and you don't want to get caught in the rain). In May, a light spring jacket or a mid-weight sweater is probably the heaviest thing you'll need. You won't need these in June. Bring some shorts/skirts and hope for great weather. If you are caught without an umbrella, buy a cheapie at the ubiquitous street vendors that pop up at the first drop.
Cost: Flights & hotel prices head north in the spring, but the heaps of tourists don't descend upon the city until summer. That doesn't mean things are a bargain, not by far. You have average odds at getting same day half price Broadway show tickets at TKTS booths.
Seasonal things to do: Roaming Central Park is absolutely essential. Walking over the Brooklyn Bridge (and hopping a subway back) is fantastic on a sunny day. The Tribeca Film Festival extends into May. Fleet Week occurs the week before Memorial Day weekend. Definitely catch a Mets or Yankees day game. Head to the Belmont Stakes in June and hope a Triple Crown winner is still possible. Watch/experience the National Puerto Rican Day Parade down 5th Ave in June. Mid-June features the Museum Mile Festival on the east side of the Park. Late June features the Jazz Festival at multiple sites (Carnegie Hall, Bryant Park, etc.), as well as Lesbian & Gay Pride Week, which culminates in a large parade.
Weather: Hot, humid, sticky, sometimes oppressive. And that's outside, never mind the subways. Temps range from 70-95 and can get north of 100 occasionally, but highs are usually in the mid to upper 80's. Anticipate 20 degree temperature spikes in the subways. It's rather disgusting down there, and the heat brings out the worst subway odors. Don't underestimate the concept of humidity: it can make a warm day feel much hotter.
What to Wear: Bring an umbrella and anticipate torrential downpours. Otherwise, wear light clothing: natural fibers are best, especially cotton and linen.
Cost: Expensive, but residents scatter for the beaches (Hamptons!) on the weekends, which means that prime restaurants are more available on the weekend (though some might close Sunday nights because of this). They're not cheap. It just means you can probably get in without reserving weeks in advance. You can be disappointed trying to get same day half price Broadway show tickets at TKTS booths, but you can wait in Central Park in July for same day free Shakespeare in the Park tickets.
Seasonal things to do: Potential visitors are often intimidated by the weather in New York at this time of year, but it is a shame that they are: this is the time of year when the most activities are available, indoors and outdoors.
The highlight of the summer is most certainly Macy's 4th of July Fireworks show, when the sky lights up like a million candles. The best place to view the show is along either side of the East River, near the Brooklyn Bridge.
Roaming Central Park is essential. Sheep Meadow becomes a sunbathers' paradise and other smaller parks like Madison Square Park are no slouches for sun-worshippers either. Listen to music at Central Park SummerStage or Celebrate Brooklyn! In Prospect Park. On the west side of Manhattan, get to River Flix at the Hudson River Park. Harlem Week runs through the month of August. Take in a cooler Mets or Yankees night games. Enjoy a cone from the Van Leeuwen Artisan Ice Cream truck. Check out the movie theatres to see summer blockbusters that may not be available in Europe or Asia for some time after your visit.
The U.S. Open Tennis Tournament kicks off in late August out in Flushing, Queens. Get to the Bohemian Hall & Beer Garden out in Astoria, Queens on the way back. It's the city's largest outdoor beer garden, and beer is cheap by NYC standards at ~$12 a pitcher for imports! If you are roasting like a hot dog at a barbecue, head to Coney Island or the Rockaways, in Queens, for the beach. The Bronx Zoo is nice and shady even on the hottest days. It is one of the largest zoos in the nation, with some air-conditioned attractions.
Also for families, renting a car or consulting a site like Hopstop for a day trip may be in order: a large amusement park, Six Flags Great Adventure in Jackson, NJ, is about an hour outside of Manhattan. This park features a water park, plenty of children's rides, and for big kids 13 thrilling roller coasters.
Weather: Starts off hot, humid, sticky, & uncomfortable., but ends a bit chilly. From Sep 1 - Sep 20, anticipate 70-80 degree weather. From Sep 21 - Oct 10, expect 70 degree highs. Beyond that, expect the highs to be in the 50-70's. Halloween has been known to be in the upper 30's or lower 60's
What to Wear: Bring summer clothes with an extra layer or two depending on how close to Halloween you come. If you're coming in the back half of October, don't expect to wear shorts, and you might not always need a jacket, but you should probably have one. And oh yeah, bring an umbrella because you'll be walking a lot.
Cost: Labor Day through New Year's is the peak tourist season in New York, and prices reflect this. The very end of October and the beginning of November are especially expensive due to the NYC Marathon.
Seasonal things to do: Labor Day weekend is rather quiet in the city, with residents still at their summer houses. The San Gennaro festival in Little Italy is the place to be in early September for fantastic food. September 11 is a solemn day in the city. The morning usually features a memorial service to the fallen victims and heroes of that day. The night is usually marked by the Tribute in Light, during which large banks of spotlights are shined into the night sky close to where the Twin Towers used to stand. There's great viewing anywhere within several miles of the city, but the best views are from across the rivers either in Brooklyn or New Jersey (Hoboken or Jersey City).
The back half of September and first half of October plays host to the New York Film Festival at Lincoln Center. The Columbus Day Parade happens around Columbus Day, as one might anticipate. If the Mets or Yankees have made it to the playoffs, try to get out to see a game. In September, football season begins, so maybe head to the Meadowlands for a Giants or Jets game. October goes out with a bang with the Greenwich Village Halloween Parade, with hundreds of folks dressing up in outrageous costumes, and even more people lining the streets. (There's always a parade in NYC in case you haven't noticed.) Late October is also the start of fall foliage season, so take a car or ferry ride up the Hudson and do some leaf peeping.
Weather: Expect highs in the 40-50 range in November and 30-40 range in December. It can be freakishly warmer or colder here and there, but it's not likely.
What to Wear: Bring a heavier jacket and consider a hat, scarf, and gloves. Bring an umbrella because you still have to walk to and from subway stops. It's much harder to catch a taxi in the rain, so if you're going to be standing around trying to hail one, you might as well be dry..
Seasonal things to do: The Radio City Christmas Spectacular starts in November, well before Christmas, so go early for cheaper tickets and capture the Christmas spirit. The marathon happens at the beginning of November. There's yet another parade on Veteran's Day, but the bigger parade is Thanksgiving Day. The biggest parade might be that of stampeding shoppers on Black Friday, the day after Thanksgiving, in all the retail stores around New York. Many have early morning sales that lead to large lines that rush through the doors before dawn.
Rockefeller Center gets its tree at the end of November, and has a huge tree lighting ceremony. Weather permitting, ice skating beneath it starts. And then there's this little thing to close out the year called New Year's Eve in Times Square. A few people have been known to show up now that the word has gotten out. Football season is in full swing, so catch a Giants or Jets game. Basketball season starts, so maybe a Knicks or Nets game is on the menu. On Christmas Eve, Jewish New Yorkers traditionally eat Chinese food and go to the movies. On Christmas Day, you can find many ethnic restaurants open around the city.