As Seattle sweats through a summer that is giving signs of being among the hottest on record, those who have eschewed air conditioning (eh, it's only used 3 days a year!) or live in a place where air conditioning is not an easy option, such as high-rise condo buildings that don’t allow window units and won't work well with portable air conditioners, might now be wondering what their options are.
Some have said they tough it out with a fan in front of a bowl of ice, but that's probably getting old, especially at night as the heat stretches from days to weeks.
I've had a few people ask me if "swamp coolers" or the more technical "evaporative coolers" would work as an alternate. They're usually cheaper than an air conditioning unit, can be ordered online, and some are portable and can work in a small room, such as a bedroom, to survive the heat until September... or October. Or 2016.
But before you think, "wow, why didn't I think of this earlier?" or "why hasn't anyone else thought of this?" there's a reason: Swamp coolers aren't exactly a best fit for Seattle's climate.
Swamp coolers rely on dry air to work their magic using the same process that your body uses to cool off -- the power of evaporation. When you sweat, the process of the sweat evaporating off your skin saps heat energy from the nearby air making it cooler. A swamp cooler takes the hot air and runs it through essentially a wet cloth. As the water evaporates off the cloth, it cools the surrounding air, which the machine then blows into your room.
(Incidentally, this is also the same process of how it snows in the winter here when it's a few degrees above freezing. The rain falls from the cloud into drier air, the rain evaporates, the temperature drops, and now it's freezing and it turns to snow. And you're welcome for this trip down memory lane of what freezing temperatures feel like.)
Swamp coolers work well in the Desert Southwest, where humidity is low and the evaporative cooling process is efficient. The exception is during the monsoon season (like now) when they get tropical moisture and the humidity climbs. Then, you have to resort to traditional air conditioning or job searches that require relocation somewhere north or west.
But if you've ever gone to the southeast, you know that sweating doesn't help much. The warm and muggy air is already holding a lot of moisture, so the evaporation process is much less efficient, which is why 87 degrees in a dry San Diego feels manageable, but 87 degrees in Atlanta is like a small step above walking on glass.
So swamp coolers, ironically, are no help in the swampy air of the muggy southeast. (They really should be called "desert coolers." Or "dessert coolers" because at least for me, that garners thoughts of ice cream, and....mmmm, ice cream on a hot day....)
What about Seattle? We're on the fringe.
With our marine climate, humidity is typically higher to where evaporative cooling isn't as effective, but then again, that same marine climate keeps temperatures from really needing it in the first place.
But what about when it gets hot? Will they work then?
It depends on the type of heat wave we have.
In most summers, when it gets over 87-90, it's due to an east wind that dries out when it sinks down the western slopes of the Cascades. If you hear us talk about "thermal trough" or "heat low" or "east wind heat event", the humidity is expected to be rather low and swamp coolers would likely work. I looked up one of those such days, July 8, 2010, which had a high of 95 and a dew point of 42. Swamp coolers would have worked OK then.
But this summer, we've been hot without the drying power of an east wind, so our humidity has been higher than usual. You might have noticed it this summer, but so far we've been fortunate that while the humidity is higher, we're not to really muggy levels, save for the days when we had a chance of thunderstorms.
In doing some online research, it seems swamp coolers begin to lose effectiveness when the dew points -- the temperature at which air saturates (more information on dew points here) reach about 55-60.
With several of the hot days this summer, dew points in the Puget Sound region have ranged from about 50-58 -- it's been a bit in flux as winds are weak and variable, and some days and nights are catching a little more humid marine air than others. Wednesday was 90 degrees with a 55 dew point. Tuesday was 87 degrees with a 57 dew point. Monday night the dew points were in the upper 50s and even touching 60, which meant swamp coolers were little to no help.
And if it's too humid already, swamp coolers will have an opposite effect of not only failing to do much cooling, but will make it feel muggier. So if you miscalculate, now your home is not only warm but humid and you're likely to run straight to that store's website and give the product a 2 star review claming you ordered a swamp "cooler" not a swamp "heater" and why would someone design a product to make your house feel more like Bourbon Street?
Other nights the dew points have managed to drop to around 50, which probably would have been cool enough to work. Then again, if dew points are lower at night, it'll allow temperatures to cool a bit more at night in which case the fan in front of the window trick might work OK too.
Bottom line: Swamp coolers probably aren't the best option as they would only work well in certain heat situations. Although in those few situations, it might be worth it, but this summer, they probably wouldn't have been too much of a help so far. Traditional air conditioning is still the best option in this climate if you can find a way to swing it and if that's not an option, the fan with the ice trick just might have to do, along with a countdown clock to September 21.