A stabilizing westerly flow will return to the region Thursday, knocking out the afternoon thunderstorm development, and bringing back sunny and dry conditions. Afternoon winds will kick up to the 10-15 mph range with gusts to 30 mph. Some haze and smoke is possible in varying amounts. Sunny weather will stay in the region through the middle of next week with highs ranging from the mid to upper 90s throughout.

So why does humidity make such a difference in how hot it feels? That all has to do with how our bodies cool themselves.

When we get hot, our brains (marvelous organs they be) send a signal to our sweat glands to open up and wet down our skin. As the sweat evaporates, it draws heat out of our skin in order to provide the energy necessary to turn liquid into vapor. For the real geeky of you out there, it’s called the heat of evaporation. The faster the sweat (water) evaporates, the faster we cool down. In dry air, water evaporates much quicker than when the air is moist, and the cooling process is much more efficient. When it is muggy, we keep sweating, but since very little of it is evaporating, we don’t get cooler.

We just get smellier.

So far it has been a pretty dry summer, with only a few patterns that produce thunderstorms. We may break back into the pattern briefly Tuesday as a light southerly flow could bring up some monsoonal moisture as far north as the Reno area, although it appears the bulk of the action will be in the mountains and to our south. High temperatures will top out in the mid-90s most of the week, before climbing into the upper 90s by the weekend. A slight chance of Tuesday thunderstorms drops out as we will go back to mostly sunny conditions for the second half of the week.

As I mentioned, we have been pretty darn dry this summer. Because we are so arid around here, I don’t get asked the following question that often, but we aim to please:

“Hi Mike… Can you explain the “Heat Index” to me?”

I may have given some of it away by mentioning our relative dryness, but the Heat Index is sort of the summer’s equivalent to the wind chill in the winter. Just as wind makes cold temperatures feel even colder, high humidity makes hot temperatures feel even hotter. The Heat Index is an attempt to take humidity into account. The exact formula used to calculate Heat Index would make most of our heads spin, so I won’t bother putting it down. But tomorrow, I’ll give you some examples.

Smoke, haze and near to record temperatures will stick around the region for the foreseeable future. Light morning winds and mild afternoon breezes will do little to flush out the smoke already in the region, and the dominating ridge of high pressure is showing no signs of going anywhere anytime soon. Low triple digit highs on Thursday will ease back into the mid to upper 90s by the weekend.

So what are the ingredients that go into the creation of lightning (either cloud to ground or cloud to cloud)? What occurs in both cases is the vertical motion of the strong updrafts creates a separation of electrical charges…. Positive on the tops of the clouds, and negative on the bottom. Envision a giant Duracell Battery and you’ll get the general idea. On a cloud to ground strike, the negative charge on the bottom of the cloud induces a positive charge on the ground, and since nature abhors big imbalances like that, there is a discharge to neutralize the electrical potential. The cloud to cloud does essentially the same thing, but the negative bottom of one cloud discharges into the positive top of another.

The heat will continue in triple digit realms for another couple of days, accompanied by generally light winds, the lack of which will be helpful for the firefighting efforts, but will be unlikely to do much to clear up our poor air quality. A slow cooling trend into the weekend will drop the highs back into the mid-90s by the first of next week, and may allow just enough afternoon breeze to help clear up the air somewhat by the weekend. At this time there doesn’t appear to be much of a chance of getting any showers for the next week, although occasional cloudiness could pop up.

Yesterday we talked about heat lightning. Steve followed up with this: “What is the difference in the “ingredients” that go into the thunderstorm “brew” that ends up producing a storm full of cloud-to-ground bolts vs. a storm producing cloud-to-cloud bolts?”

The ingredients are really the same. In fact, most storms that have cloud to ground strikes will also have a lot of cloud to cloud strikes as well. Tomorrow, I’ll talk about just what those ingredients are.

Strong winds will accompany a cooling temperature profile to create a very dangerous fire situation through Saturday. A Red Flag Warning is in effect for nearly all of northern Nevada and northeastern California, with winds in the afternoon expected to gust to as high as 40 mph in the foothills and wind prone valley locations. Humidity will likely stay below 15%. On a positive note, high temperatures could actually fall to below average to the low 90s over the weekend, before climbing back up to triple digits by the middle of next week.

Yesterday, I mentioned that while Reno set temperature records for the month of July, it wasn’t necessarily the warmest July ever. I’ll start by saying that this was a hot month…very hot by any metric. But when comparing temperatures over nearly 150 years, at the very least, the thermometer should remain in the same spot. But Reno’s has moved over a half a dozen times, finally landing at the airport in the 1940s (and it has moved to several different places at the airport itself since then). But perhaps even more significant, the environment at the airport thermometer has changed dramatically, moving from irrigated alfalfa fields 40 years ago to now being planted right in the middle of the airport tarmac. Such a change makes a huge difference, at times creating a 5-10 degree bump in the temperatures at the airport compared with the surrounding undeveloped areas.

So was this the hottest July or not? Unfortunately, there’s really no way to say for sure. I think it’s safe to say it was the hottest July since they moved the thermometer to it present location between the runways (about 15 years ago), but beyond that, it’s not as objective an answer as you’d like.