What is the cheapest airline to fly from Islip, New York to Seattle round-trip?

Flying on Southwest is currently your cheapest option to Seattle, with prices starting at $385.

In terms of precipitation, rainfall in Seattle ranges from 0.7 - 6.6 inches per month. November is typically the wettest month, when rainfall can reach 6.6 in. July is typically the driest time to visit Seattle when rainfall is around 0.7 in.

If weather is an important factor for your trip to Seattle, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 66.2 F. Travelers looking to avoid the cold should look outside of December, when temperatures are typically at their lowest (around 41.0 F).

How far in advance should I book a flight from Islip, New York to Seattle?

To save on the cost of your flight from Islip, New York to Seattle, book at least 50 days before your planned departure. Booking around this time can save you about 75% on the cost of this flight compared to booking a flight leaving this week. We have found prices from $469 if you need a flight within two weeks. For flights within the next 72 hours, you can find tickets from as low as $687.

What is the cheapest month to fly from Islip, New York to Seattle?

September can be a great time to fly to Seattle from Islip, New York with a flight ticket averaging about $416. Cheapflights users have found deals in the month of September for as cheap as $169. The most expensive prices can be found in the month of December.

What is the cheapest time of day to fly from ISP to SEA?

When flying from Islip, New York to Seattle, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.

Can I find deals for flights from Islip to Seattle that include hotel bookings?

Yes. In addition to deals on Islip to Seattle flights, Cheapflights offers vacation packages that include both flights and hotel.

How can I find direct flights from Islip to Seattle?

After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Islip to Seattle.

Can I find deals for business class flights from Islip to Seattle?

Yes. Cheapflights offers flight deals from Islip to Seattle by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

$167+ Flights from Islip, NY to Seattle

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Cheap flight deals from Islip to Seattle

Round-trip from	$385 (Southwest)
One-way from	$167 (Southwest)
Popular in	December
Cheapest in	September
Average price	$507

From Islip Long Island to Seattle/Tacoma Intl

Search Deals

One-way flight from Islip Long Island to Seattle/Tacoma Intl

Search Deals

Highest demand for flights based on searches. 5% potential increase in price ($24 potential increase over avg. RT price).

Search Deals

Cheapest flight prices on average. 3% potential price decrease ($14 potential savings vs. average RT price).

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Average for round-trip flights in July 2025

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Find flight deals from Islip to Seattle

Cheapest flights from Islip to Seattle
Explore the most affordable flight options available from Islip to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 29, 2025.

Tue 9/26:05 amISP - SEA

1 stop8h 10mSouthwest

Tue 9/911:10 pmSEA - ISP

2 stops9h 45mSouthwest

Deal found 7/27

$385

Wed 8/132:55 pmISP - SEA

2 stops20h 07mMultiple Airlines

Sun 8/1711:59 pmSEA - ISP

2 stops12h 22mMultiple Airlines

Deal found 7/29

$989

Best flights from Islip to Seattle
Discover carefully curated flight deals from Islip to Seattle that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated July 29, 2025.

Tue 9/26:05 amISP - SEA

1 stop8h 10mSouthwest

Tue 9/99:10 pmSEA - ISP

1 stop11h 45mSouthwest

Deal found 7/27

$385

Wed 8/132:55 pmISP - SEA

2 stops20h 07mMultiple Airlines

Sun 8/1711:59 pmSEA - ISP

2 stops12h 22mMultiple Airlines

Deal found 7/29

$989

Last-minute flights from Islip to Seattle
Discover last-minute flight deals from Islip to Seattle. Data last updated July 29, 2025 and is based on user searches.

Wed 8/66:05 amISP - SEA

1 stop8h 10mSouthwest

Sun 8/1011:10 pmSEA - ISP

2 stops9h 50mSouthwest

Deal found 7/27

$852

Wed 8/62:55 pmISP - SEA

2 stops20h 07mMultiple Airlines

Sun 8/105:30 pmSEA - ISP

3 stops18h 49mMultiple Airlines

Deal found 7/27

$1,121

Wed 8/132:55 pmISP - SEA

2 stops20h 07mMultiple Airlines

Sun 8/1711:59 pmSEA - ISP

2 stops12h 22mMultiple Airlines

Deal found 7/29

$989

Tue 8/196:05 amISP - SEA

1 stop8h 10mSouthwest

Mon 8/259:20 amSEA - ISP

2 stops10h 35mSouthwest

Deal found 7/27

$504

One-way flights from Islip to Seattle
Search for one-way flight options from Islip to Seattle. Find affordable one-way fares based on user searches. Data last updated July 29, 2025.

Wed 9/176:05 amISP - SEA

1 stop8h 10mSouthwest

Deal found 7/28

$167

Fly from

Fly to

Route

Depart

Return

Price

IslipSeattle

ISP - SEA

ISPSEA

Islip Long Island

Tue 9/2

6:05 am-11:15 am

1 stop8h 10m

Seattle/Tacoma Intl

Tue 9/9

9:10 pm-11:55 am

1 stop11h 45m

$385

IslipSeattle

ISP - SEA

ISPSEA

Islip Long Island

Wed 8/13

2:55 pm-8:02 am

2 stops20h 07m

Seattle/Tacoma Intl

Sun 8/17

11:59 pm-3:21 pm

2 stops12h 22m

$989

IslipSeattle

ISP - SEA

ISPSEA

Islip Long Island

Wed 9/17

6:05 am-11:15 am

1 stop8h 10m

$167

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/28

Best time to book a flight from Islip to Seattle

Have a flexible travel schedule? Discover the best time to fly to Seattle from Islip with our price prediction graph.

Estimated round-trip price

Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from Islip to Seattle

What is the cheapest month to book a flight from Islip, New York to Seattle?

Currently, January is the cheapest month in which you can book a flight from Islip, New York to Seattle (average of $238). Flying from Islip, New York to Seattle in June is currently the most expensive (average of $389). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

Reviews of airlines servicing Seattle

Read through reviews of airlines operating flights from Islip to Seattle, such as Southwest. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.

Southwest

8.0

Very good

4,238 reviews

Reviews

1 / 20

8.0

Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.

Southwest

8.0

Very good

4,238 reviews

Southwest

8.0

Very good

4,238 reviews

Reviews

1 / 20

8.0

Excellent

Gina,Jul 2025

LAS - DEN

Related info for your journey

What is the cheapest airline to fly from Islip, New York to Seattle round-trip?
Flying on Southwest is currently your cheapest option to Seattle, with prices starting at $385.
Can I find deals for flights from Islip to Seattle that include hotel bookings?
Yes. In addition to deals on Islip to Seattle flights, Cheapflights offers vacation packages that include both flights and hotel.
How can I find direct flights from Islip to Seattle?
After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Islip to Seattle.
Can I find deals for business class flights from Islip to Seattle?
Yes. Cheapflights offers flight deals from Islip to Seattle by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.
What is the cheapest month to book a flight from Islip, New York to Seattle?
Currently, January is the cheapest month in which you can book a flight from Islip, New York to Seattle (average of $238). Flying from Islip, New York to Seattle in June is currently the most expensive (average of $389). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

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Other flights to Seattle

Top airline flying from Islip to Seattle

Airline	Cheapest	Average	Flexibility	On-time
Southwest	Cheapest$356	Average$564	FlexibilityNo cancel fee	On-time63%

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$167+ Cheap flights from Islip, NY to Seattle (ISP - SEA)

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 9/17. Fares are subject to change and may not be available on all flights or dates of travel.

Find cheap flights from Islip to Seattle with Cheapflights

1. Tell us where you want to go

2. Select your favorite providers

3. Compare prices and book

Cheap flight deals from Islip to Seattle

Round-trip from

One-way from

Popular in

Cheapest in

Average price

Find flight deals from Islip to Seattle

Cheapest flights from Islip to SeattleExplore the most affordable flight options available from Islip to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 29, 2025.

Explore the most affordable flight options available from Islip to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 29, 2025.

Cheapflights Fare Finder

Use the filters below to find and compare flights from Islip to Seattle that are best for you.

Best time to book a flight from Islip to Seattle

Have a flexible travel schedule? Discover the best time to fly to Seattle from Islip with our price prediction graph.

Cheapflights Insights

Everything you need to know about your flight from Islip to Seattle

What is the cheapest month to book a flight from Islip, New York to Seattle?

Reviews of airlines servicing Seattle

Read through reviews of airlines operating flights from Islip to Seattle, such as Southwest. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.

Related info for your journey

Find useful and relevant information for your journey from Islip to Seattle. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

What is the cheapest airline to fly from Islip, New York to Seattle round-trip?

Can I find deals for flights from Islip to Seattle that include hotel bookings?

How can I find direct flights from Islip to Seattle?

Can I find deals for business class flights from Islip to Seattle?

What is the cheapest month to book a flight from Islip, New York to Seattle?

Traveling to a place near Seattle?

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for Islip to Seattle

See prices for flight routes from nearby airports that may be better suited for you.

Top airline flying from Islip to Seattle

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Book with Flexibility

Travel Smart

Cheapest flights from Islip to Seattle
Explore the most affordable flight options available from Islip to Seattle. Find the lowest fares from popular airlines and budget airlines, with prices last updated on July 29, 2025.