If you wanted to play it safe, why not cover things with cardboard boxes, or tent over the bed with a blanket? The Spirea and blueberries would just lose newest leaves, but the ranunculus, heather and lavender, depending on which species you have, could eat it.

If the Ranunculus is R. asiaticus out of a greenhouse, it could have problems with cold weather. The others should all be hardy, unless any have come out of a greenhouse also and are unseasonably advanced in growth and therefore more tender than they would otherwise be at this time of the year.

Last forecast I saw for up here for coming week did not include frost or snow, just showers. Hard frost would be the main cause for concern, rather than snow - which protects plants from cold by insulating them.

Snow not likely. Portland's record low went from 19 for March 4th to 28 for March 5th.

Forecasters are split for next week though; lowest forecast I've seen is 32, most are saying normal temps 54/38.

If you see it clearing off in the evening early next week, you might want to cover the smallest stuff so you can sleep well.

Yesterday, the forecast for my lat/long (KOMOTv weather service) was reading Mon morning 5 AM, 25F with wet snow.
Causing panic of course.

That's been softened a little this morning and they've bumped up the predicted temp by 4F, hopefully by later today it will be even higher. Light frost is fine. A little wet snow OK, I've seen that first week of March more than once. 25F would not be a welcome number.

The 7 day NOAA forecast for Portland shows NO indication or likelihood of snow. In fact, the lowest temp of the coming week is predicted to be 36F on Monday night with daytime highs in the high 40's to mid 50's.

I doubt you have much to worry about :-)

Seattle's is a bit more severe, with Monday's low predicted at 33F. But just occasional rainy periods, no snow. Morz8, the NOAA forecast for the Hoquiam area (closest station to the coast) is very much in line with that of Portland. I'd say 25F is on the overly pessimistic end of things :-)

My hope was very much that it was overly pessimistic, and I think that's going to be the case. I must feel confident, I didn't spend the afternoon throwing together makeshift cold frames or hauling out the stack of old tablecloths though I may still roll a couple of plant carts with germinating perennials into the carport. The numbers I'm getting now are more in the 31F range and only briefly that cold at right around dawn. It was that cold several mornings last week before giving way to beautiful afternoons, nothing seemed to mind the chill.

It's raining now and 48F - what a difference a day makes.

More Portland forecasters are agreeing on 33°.

The NOAA forecasts tend to be conservative while the TV people play up weather events with a 5% or 10% chance.

TV guy on Saturday night said 3" snow in the Willamette Valley Tuesday. Radio all day Sunday makes no mention of it. I think some agency should send forecasters door-to-door daily (like the frequency of window salesmen) and really ham it up.

Just had a brief snow flurry on Camano Islands (Island County, WA, northwest of Everett and southeast of Mount Vernon).

Just hailed like hell here in Northeast Portland for about 9 minutes...plum trees hard hit, most everything else looks ok. Now the sun's coming out. Go figure...must be spring.