Where should we start with the rain? I grew up in Maryland and if you asked anyone in Maryland if it were a rainy place, they would probably say “No”. If you ask the people of Seattle “is it a rainy place?”, most people you survey would say “Yes!” In actuality, most of Maryland receives about the same amount of rain as Seattle. It is really about when and how the rain falls. In the Seattle area, we can get drizzle that goes on for days and barely add up to an inch. Then in the summertime we can go three months without rain. August averages less than a 1/2” of rain a year. September about 1″. In places like Maryland, it’s relatively dry in the Autumn and Winter with heavy thunderstorms in the summer dumping inches at a time. It’s apples and oranges.
The Puget Sound region gets compared to Eastern Washington, where 99% of the grapes in the state are grown, for good reason, it’s where the bulk of the wine industry is. I get that. Eastern WA gets so dry because of the rain shadowing effect of the Cascade mountains. The central Yakima valley only receives 5-6″ of rain a year. In fact, grape vines, apple trees, hops or whatever you grow over there could not survive without supplemental water. We don’t have the problem over here, as most of our vines are not irrigated and survive on their own.
Let me get on my soapbox now. Many times people in places of authority in the wine world negatively compare us to Eastern Washington when we should be compared to Northern Oregon or Europe. I routinely have people ask me how we can grow grapes in such a rainy climate (usually during a nice summer day) and I have to explain why we can where this never seems to be an issue with growers in Eastern Washington or even in Oregon. The fact is that most of the Puget Sound region is drier than the Willamette valley, just a tad cooler.
Looking at this little graphic that the Washington Wine commission put together (one of many I have seen from that that misrepresent the rain). Shows 40″ of rain somewhere over the mountains. That number should be right over Seattle. The Cascades get hundreds of inches of rain a year as do the Olympic Mountains. Then to the right there is a large ball of sun in Eastern Washington. Not over the Puget Sound region. I don’t know if this is just from ignorance or lack of research but after 20+ years of doing this and seeing the same type of graphic over and over it makes you wonder… OK off my soapbox.
The simple fact is that the Puget Sound receives less rain annually than many other well-known grape growing regions, and we get less than other growing areas most during the most important growing time of the year (April-October). Rainfall averages for the Puget Sound range anywhere from 16″ in Sequim, to 66″ in Concrete. Keep in mind that less rainfall doesn’t always mean a better place to grow grapes. Generally, it’s much cooler in the areas that have less rain than those that have more in the Puget Sound AVA.
The problem with rain in the Puget Sound AVA is when it comes, not how much. There are two critical times of the year that the rain comes at the wrong time many years, June and October. When rain comes in June, this can coincide with flowering. It’s essential that the flowers have almost completely dry and sunny conditions for pollination. If it rains during flowering, fewer flowers are pollinated and therefore fewer grapes will be formed. There have been years when I have lost all my Chardonnay because of a lack of grapes because Chardonnay flowers a week or so before Pinot Noir.
The next critical time for rain is actually anytime the grapes have turned color but the closer to picking the worse it can be. Unfortunately, the rains start to come more frequently in September and get more frequent through October. Rain really ramps up in mid-October and if you don’t get grapes picked by then, usually they will rot on the vine. Unless of course if you grow a grape like Regent or Rondo which is very resistant to rot. Pinot Noir is a very thin skinned grape and rots very easily.
But in general the Puget Sound region is quite a bit dried DURING THE GROWING season when it’s most critical that it’s dry.
Here is a comparison of seven well known growing regions against Seattle. You will see Seattle gets less rain during the growing season than all of these cool climate growing regions. Less rain usually means less disease and more sunlight. In millimeters per month
| Location | Apr | May | Jun | Jul | Aug | Sep | Oct | Total |
| Loire | 47 | 53 | 50 | 42 | 41 | 41 | 74 | 348 |
| Chablis | 51 | 59 | 71 | 63 | 58 | 53 | 69 | 424 |
| Bordeaux | 67 | 65 | 60 | 52 | 47 | 55 | 81 | 427 |
| Burgundy | 50 | 55 | 69 | 62 | 61 | 54 | 78 | 429 |
| Nantes | 56 | 56 | 50 | 53 | 50 | 50 | 89 | 404 |
| Champagne | 47 | 54 | 53 | 67 | 58 | 42 | 67 | 388 |
| Rheingau | 36 | 41 | 53 | 53 | 53 | 46 | 51 | 333 |
| Seattle | 58 | 46 | 36 | 15 | 18 | 43 | 74 | 290 |
Here is a good high resolution rainfall map of the Puget Sound region. You’ll notice that the closer to the water, generally the lower rain totals and this is from the rain shadowing effects.
The area near Sequim and Port Townsend to Whidbey Island and the San Juans get less than 30 inches a year and in some places less than 20″. A large vineyard on Lopez Island needs supplemental water some years. But generally the low lands get less than 50″ a year which is a key figure. More than 50″ a year and your grapes can be adversely effected by the rain in the spring and fall and also from standing water in your soil. You’ll notice how closely the Puget Sound AVA boundaries follow the 50″ line and that is on purpose.
So, next time someone tries to tell you that it’s really wet in Seattle, it’s not really that wet compared to many other places in this country and the world, it just seems that way in the middle of January when it can rain for days on end.