June and September are the best months for an outdoor party in Stony Brook, with average highs of 77 and 75 degrees and fewer 90-degree days than July or August.
The numbers come from NOAA's 1991 to 2020 climate normals for Long Island MacArthur Airport in Islip, a long-record station on Long Island with a full 30-year history. It is not in Stony Brook, so read the figures as the climate of the area. They are averages, so any one year runs warmer, cooler or wetter, and the forecast for your week decides the day.
How warm and wet is Stony Brook from May to October?
Average highs climb from 68 degrees in May to 83 in July, then fall to 64 by October. The table gives NOAA's monthly normals in degrees Fahrenheit, with the average number of days that bring 0.10 inch of rain or more and the average number of days with a high of 90 degrees or more.
| Month | Average high | Average low | Rain days (0.10 in. or more) | Days at 90 or higher |
|---|---|---|---|---|
| May | 68.3 | 50.8 | 6.6 | 0.3 |
| June | 77.2 | 60.9 | 6.2 | 1.5 |
| July | 82.8 | 67.3 | 5.5 | 4.1 |
| August | 81.4 | 66.0 | 5.7 | 2.2 |
| September | 74.8 | 58.9 | 5.5 | 0.2 |
| October | 64.1 | 47.3 | 5.6 | 0.0 |
Rain barely changes from month to month. May through October average 5.5 to 6.6 rain days a month, and across the whole year the range runs from 5.5 days in July and September to 7.8 in December. The driest month still brings a tenth of an inch of rain or more on 5.5 days, so no month is safe to book without a plan.
Which month is best for a backyard pizza party in Stony Brook?
June and September. June averages a high of 77.2 and a low of 60.9, and September a high of 74.8 and a low of 58.9. June averages 1.5 days at 90 degrees or higher and September 0.2, against 4.1 in July and 2.2 in August.
July and August are the warmest months, with average highs of 82.8 and 81.4. The National Weather Service heat index measures how hot it feels with humidity included, and the NWS says full sunshine can add up to 15 degrees to it. Its Upton office, which forecasts for Suffolk County, issues a Heat Advisory when the heat index is forecast to reach 95 to 99 degrees for two or more days, or 100 to 104 degrees for any length of time. For a July or August date, put shade and water where guests gather and plan the party for the evening.
May and October are the cooler months. Average highs are 68.3 and 64.1 and average lows are 50.8 and 47.3, so guests at an evening party in either month want a jacket more than shade.
Does hurricane season affect a Stony Brook party?
It can from June through November. The National Hurricane Center says the Atlantic hurricane season runs from June 1 to November 30, with its peak on September 10 and most activity between mid-August and mid-October. A September date sits inside that window, so choose a backup date when you book.
How do you plan an outdoor pizza party around rain?
Agree on a rain plan with your caterer when you book the date, because no month in the table is dry enough to skip one. Ask any caterer what happens to the date, the start time and the setup in rain, and get the answer in writing.
Then settle three things yourself: the hour you will make the call, the backup date, and where guests go indoors if a storm arrives. The National Weather Service rule for thunderstorms is "When Thunder Roars, Go Indoors," and it says there is no safe place outside when thunderstorms are in the area.
We bring the wood-fired oven to Stony Brook, with no travel fee anywhere in Suffolk County. See our backyard party pizza catering page, then book the truck or call or text (631) 538-7596. Send your date, headcount and address and Mikey will tell you which package fits.
Sources
- NOAA NCEI: 1991-2020 monthly normals, Islip Long Island MacArthur Airport (CSV)
- National Hurricane Center: Tropical cyclone climatology
- National Weather Service: Heat index
- National Weather Service New York, NY: Extreme heat page
- National Weather Service: Suffolk County forecast zone
- National Weather Service: Lightning safety
