> 1. Which is better in terms of weather?

Olympic NP is MORE LIKELY to have rain, but there's no guarantees. It could be drizzling in Olympic and dry in Rainier, or dry in Olympic and a thunderstorm at Rainier.

> 2. Is either of the drive from Seattle windy with switchbacks?

Mount Rainier is a mountain. As such, driving to it involves going higher in elevation -- which means switchbacks.
You can get to some interesting areas of Olympic with hardly any elevation gain at all. But to get to Hurricane Ridge will mean some switchbacks.

> 3.

There are no budget hotels in or that close to Mount Rainier. It's very essence and attraction is that it is far from tourist development. If you stay in Port Angeles, on the other hand, you'd be somewhat close to Lake Crescent and Hurricane Ridge. This pdf should help:
http://www.nps.gov/olym/planyourvisit/upload/OLYM_map.pdf

Snow in the Cascades is especially deep this year. By mid-June there will still be several feet of snow on the ground at the Paradise and Sunrise visitor centers on the mountain (parking lots and lodge areas will be plowed and clear, but many trails etc. will still be inaccessible.

Olympic NP has much more variety - low-elevation rain forests, great wild beaches, and superb mountain scenery (Hurricane Ridge near Port Angeles.) The Olympic Mountains actually block a lot of the moisture from reaching the eastern and northeastern parts of the Olympic Peninsula (the area around Sequim - "Skwim" - being called the "banana belt") so you can stay in a relatively dry area if you choose.

But the park occupies the middle of the peninsula, so to visit the park's various areas you need to travel around the periphery, which can require an hour or more in the car to get from one area to another. I'd say 3 days is a minimum, but to be frank in June I think it's your best option.

One thing to note is that most people will tell you that summer in the Pacific NW doesn't really start until July 5. Not always the case, but just worth keeping in mind.

I would choose the Olympic peninsula for its variety, which includes the various sites in the national park. The greater possibility of rain means that there is a wonderful rain forest to be visited on the western side. Neah Bay has an interesting museum that contains an Indian village that was buried in mud a few hundred years ago, thus preserving the wooden structures that would have otherwise rotted away. From Neah Bay there is a nice hike through the forest to the western-most point of the lower 48 States.

http://www.flickr.com/photos/mksfca/sets/72157622991196341/show/with/4235004880

1. Consider that the rainiest town in the continental U.S. is Forks, WA, which is just 5 or 6 miles from O.N.P.... so give the rain question to ONP hands down

2. Don't think you're going to worry too much about windy roads with switchbacks unless you leave the most probable path. Indeed you can SEE the road ahead seemingly 'switching back' when, say, leaving Paradise, Mt. Rainier... but these don't happen quickly or repetitively, and you are not perilously near to a cliff or anything.

3. From all you say, I think, maybe 3 nights in Port Angeles/Port Townsend/Sequim area might suit you best... and/or 1 of the nights in Forks before you continue the full circuit of the Olympic Peninsula.

Consider that the rainiest town in the continental U.S. is Forks, WA, which is just 5 or 6 miles from O.N.P...

And the snowiest place in the USA, not just the lower 48, and one of the snowiest places on Earth, is Paradise Inn on Mount Rainier.

Thanks so very much for all your responses! Its a huge help! It seems like ONP might be a better bet given our constraints, and we just have to hope that it doesn't rain *too* much when we are there. Any suggestions for lodging in ONP?

NorthwestMale - thanks for your suggestion. Why would you pick Port Angeles over a place like Forks? I don't know much about either of the places, except it looks like Forks may be closer to some of the attractions.

Forks has changed over the years. When we were there, it was a dying lumber town with a prominent totem pole with a spotted owl on top to represent the reason for the lack of lumbering. It was definitely non-environmental and not crazy about outsiders. A friend was there recently and described it as a town that has converted itself to eco-tourism, very friendly to visitors.

If you are intent on visiting Washington State, three days in the San Juan Islands or driving the North Cascade Loop, would suit your three requirements better than ONP or Mt Rainier.

http://www.visitsanjuans.com
http://www.cascadeloop.com

Room rates will be lower in June than in July or August because our summer starts some time during the first week of July.

Other good options for you are the Oregon Coast and the Columbia River Gorge.

HTTY

PS If your idea of a vacation is to stay in mom-and-pop motels in nondescript little towns, Forks will suit you.

Happytrailstoyou - we are going to WA to visit friends anyway in June. We are definitely open to destinations other than ONP. A great day for us would be a clean hotel, good food (we are vegetarians and so sometimes find a kitchen very handy) and short or stroller friendly hikes close to the hotel. We don't do much of water sports and would prefer not to drive too much with a 3 year old, and definitely want to avoid switchbacks. Given this, would love to hear other places that would better suit us than ONP.

Check out Leavenworth WA. It is a slice of Bavaria in the Cascades. http://www.leavenworth.org/modules/pages/?pageid=52&path=37|352
They seen to have festivals and other events all through the year.

IF you are serious about alternative options, the North Cascades Highway (which I very recently mentioned in greater detail on another thread) is a great choice!

Cover it during a full day, and stay in Winthrop, WA on the other end, then perhaps drive back toward Seattle via Leavenworth.

As for Port Angeles vs. Forks... I can't give you a grand reason, but "Hurricane Ridge" would certainly be central to my thoughts, and I suspect that with roughly 6 times the population of Forks (2000 census - not 2010), Port Angeles is likely to offer more as a base camp.

Indeed I'd visit Forks, if mainly for the Twilight series fame and the "rainiest town in the lower 48" distinction. Why you could even stay at the "Dew Drop Inn" there.

I definitely do NOT have a strong preference (unless, that is, you were traveling with a gaggle of teenage girls) (which would make it Forks, hands down).

If the skies are clear and Mt. Rainier is visible from Seattle, a visit to the mountain is a great day trip from Seattle.

Also, I think a good two-night trip would be Highway 2 over Stevens Pass with a stop in Leavenworth and up 97A for great views of the Columbia River and a night at Lake Chelan. Check out this place: http://www.grandviewonthelake.com/

The next day, drive to Winthrop and spend a night at one of the many places there: http://www.centralreservations.net/lodging/methow_valley

Return to Seattle via the North Cascades Highway (Highway 20).

It is summer in June on the east side of the mountains.

HTTY

Thanks everyone! I will look into North Cascasdes and Leavenworth as well...

Because you have a toddler, expect some snow. It may be warm in Seattle or wherever you are, but it won't be, even in June, as you climb in altitude. Bring extra clothes. I know this is obvious, but bring a camera. You can tell the tourists because they take 30 pictures an hour. The locals only take 29 and hour...

Here is the answer to your main question - which park to choose. I would choose whichever has the best visibility on the day you can go. If neither has great visibility, try waiting a day if you can. The drive is worth it regardless, but on clear days it is just, technically speaking, awesome.

The first thing I would do is check the weather for Hurricane Ridge (Olympic National Park) http://www.nationalparkguru.com/olympic-national-park-hurricane-ridge-live-cam/ and for Paradise (Mt Rainier National Park) http://www.nationalparkguru.com/mount-rainier-national-park-live-cam/.

Here is your checklist:
1. Can you see the Olympic Mountains or Mt Rainier from where you are?
2. What is the weather going to be like later in the day? Check the weather report.
3. Take a look at the both the Olympic National Park and Mt Rainier cams.

You can plan your trip by knowing how to get there. For the Olympics http://www.inationalparks.com/national-parks/olympic-national-park/olympic-national-park-information/directions-to-hurricane-ridge/ and for Mt Rainier http://www.inationalparks.com/national-parks/mount-rainier-national-park/mount-rainier-national-park-information/directions-to-mount-rainier-national-park/

You said, "I have motion-sickness, so would much prefer to avoid windy roads." Umm, every time I go, there are still a few places where, if you look down a steep canyon, you will be white-knuckling it. No matter how many times you have been there. But, that beauty, and terror, is part of the trip.

Note some people have made mention that the Forks (west) side of the Olympics is wet. But the Olympic Mountains also block weather from getting to the other side and frequently places like Sequim and Port Townsend will sit in the "Blue Hole," meaning all the clouds have been blocked, and it is blue sky above these two towns.

You can read additional review at places like Yelp.
Mt Rainier http://www.yelp.com/biz/mount-rainier-seattle
Olympics http://www.yelp.com/biz/olympic-national-park-port-angeles

I'm working on a Passport in Time project at the La Wis Wis campground. We will be restoring an old Guard Station so that it can be rented probably next year.
I hope it is not too cold since I will be camping in a tent.
The campground is not officially open but there will be volunteers camping there.
I'll let you know if I see snow near US 12 northeast of Packwood. Packwood would be a good place to spend a night if you decide on Mt. Rainier.