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As an example, if you hike in The Enchantments area in Washington you will be swarmed with mosquitoes, to the point where mosquito head nets are an absolute must. On the other hand, if you hike in the Mt. Rainier national park, mosquitoes are pretty rare and I've never once had to apply bug spray. Both locations have rivers/streams and lakes but for some reason mosquito density is completely different.

Is there a rule of thumb on where mosquitoes will be plentiful? It would be useful for planning future hikes.

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  • 6
    If a guidebook/alltrails/local/etc says they will be plentiful, they will be plentiful ;)
    – noah
    Jul 27 at 21:03
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    Not obvious. I well remember stopping for gas along I 80 in eastern Wyoming , essentially no trees, dry, rolling grasslands no apparent water . It took a couple minutes for the mosquitos to find us but when they did we all ran to the car , pulled onto the interstate with the windows open to blow out the mosquitos that followed us. Jul 28 at 16:14
  • Well, typically there's not very many mosquitos in the desert...
    – nick012000
    Jul 29 at 15:11
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You probably ought to mention altitudes. Enchantments is at 1500m, Rainier's main visitor station is at 1900m. Mosquitoes, and flies, are highly altitude-dependent, as well as water-dependent. I remember bailing out early from a weeklong hike in the Pyrenees because any dips below 1000m brought deerflies. This was a crest-valley-crest-valley-... hike, I got plenty of experience of that altitude dependency.

Past that, slow-moving water, as opposed to swift rivers in steep downhill areas, is what mosquitoes prefer. Lake breeding might (I guess) be kept in check by fish.

I also think prevailing wind speed affects mosquitoes. They just don't fly very quickly so they'd get carried away by steady winds. That or wind mess with their prey-homing mechanisms.

Mosquitoes, at least in some areas, also depend on the time of day. Caribbean mosquitoes, from living 8 yrs there, are most active at dusk/twilight. So timing your trip through some known-infested areas can be useful. The few times I've had real problems in BC were in late afternoon, but I've had so few problems here that I hesitate to think much of it, especially when forest cover gets factored in.

interesting reading: https://underc.nd.edu/assets/216551/fullsize/mcreynolds2003.pdf note the remarks about temperature and the types of nearby water bodies.

At a guess:

  • regional aspects - are mosquitoes in the general area or not? I don't mean to be flippant here - Canada is known for mosquitoes in summer. Coastal British Columbia, not so much. It happens, in spots, but it's not the general expectation.
  • temperature - seasonal and altitude-dependent
  • water availability, but not a lake or river. Think puddles/swamps/stagnant pools. For areas with dry/rainy seasons - look at during/after rainy times. For temperate climates, seasonal temperature matters more.
  • time of day
  • windspeed, which you can probably gauge by regional factors and topology.
  • Tree cover/shade also seems to affect many species. I've rarely seen them in full sun, open terrain. Then again, up in the far North, an area I have no experience with, they seem to do pretty well, in areas that I assume are without extensive cover.
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  • Surprisingly mosquitoes are very common even at the top of Aasgard Pass in The Enchantments, which is at 7,800 feet/2300m. Jul 27 at 20:39
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    well, cycling BC plateau at 1500m was ok (it's dry) till Anahim Lake (1500m) - swampy area, deadly mosquitoes. Past Whistler, Pemberton's campground at 700m, also has a massive mosquito problem, near a fast-moving river. It's complex, which is I why I think this is a good question to ask. Jul 27 at 20:42
  • High enough in the Rockies and Cascades, the beautiful mountain lakes freeze completely in the winter, so no large fish populations to keep mosquito larvae in check. Hard to tell exactly which ones, except by the number of mosquitos.
    – Jon Custer
    Jul 28 at 17:43
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    Most of The Netherlands is between -10 and 300m, but the mosquito population greatly varies. Availability of water seems to be a great factor. Still, shallow water is perfect for laying mosquito eggs in.
    – Mast
    Jul 29 at 11:23
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Mosquitoes are more plentiful near water.

Life in general is more plentiful at lower elevations.

Many places have a mosquito season. In the Sierra, for example, it's usually June and part of July. It can vary from year to year depending on how wet it's been.

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Lots of vegetation coupled with high humidity creates those little pests that drive one insane.

The tundra you find in the northern regions around the world are breading grounds for mosquitos!

I worked 300 miles north of the artic circle in the brooks range of Alaska, and as long as the temperatures stayed over about 40 degrees F they just kept increasing in numbers!

Once the temperatures start reaching in the 30's they start to die off!

Good luck!

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