The city has its Cooling Centers open. You can find a list of sites at this link (you can narrow down the choices by zip code; many of the options are for seniors only).
Local options include:
• Ottendorfer Library, 135 Second Ave. between St. Mark's Place and Ninth Street — 10 a.m. to 5 p.m.
• Hamilton Fish Park Library, 415 E. Houston St. between Pitt and Columbia — 10 a.m. to 5 p.m.
(The Tompkins Square branch remains closed for renovations.)
Also listed among the cooling centers: The big new Petco on Union Square East. They are open from 9 a.m. to 9 p.m.
Outdoor city pools will stay open for any hour later (to 8 p.m.!) today and tomorrow.
You could also go old school and open a hydrant... of course, that is ILLEGAL!
But! There is a legal way to go about this. Per an article of The City yesterday:
You can put in a request to the Fire Department to open a hydrant. If it’s approved, a member of the fire department will come to fit the hydrant with a spray cap and return that same day to close it up. To request a spray cap fitting, go to your local firehouse and fill out a short form.You can find your nearest firehouse on the 311 Firehouses page. You must be over 18 years old and bring your ID with you.