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Updated 17 hours, 21 minutes ago.

The annual monsoon has officially started, although it will be days before the dust storms, thunderstorms, rain and lightning blast into the Valley.

The summer rainy season used to start and end, based on dew point readings, but last year it was decided to do it by dates -- from June 15 to Sept. 15.

Forecasters say this year's monsoon could kick into high gear at the end of June and be more powerful that normal. The key ingredient, said Arizona State University climatologist Randy Cerveny, is heat.

"You usually have to have a lot of hot weather to fire up the moisture, fire up the monsoon thunderstorms," said Cerveny.

One of the strongest storms in years packed a big punch last August when a microburst hit, tearing roofs off homes, uprooting trees and downing power lines acorss the Valley.

Cerveny said a microburst "is in essence a little air bomb that blows up out of a storm, then blasts down and hits the ground like a bomb blast."

It's not clear how this monsoon will shape up. Doug Green with the National Weather Service said early indications were that it would be a good rain producer, but now he's not sure.

"The confidence in the summer forecast for the Phoenix area is probably not as high as it was a month ago, and, even if it was confident, there's a typical variability in the amount of precipitation that occurs over the Phoenix metropolitan area, across Maricopa County," Green said.

"Last summer was a good example -- when Sky Harbor was a lot wetter than it usually is, but other sites in the Valley, not more than 5 or 10 miles to the west or to the north, were well below normal."

Green said it's important to remember that wind storms and lightning, along with extreme heat, can be deadly.

"Just be careful out there because thunderstorms -- no matter what you call them and whether it's a wet monsoon or dry monsoon -- can be very hazardous."

bla bla,

FD

Weather forecast from Arizona Central:

Temperatures will soar this weekend with highs ranging 105-110 across the Valley on Sunday. Look for sunshine with some afternoon clouds, however monsoon thunderstorms are expected to hold off until the middle of next week. Highs near 110 will continue through the rest of next week. Have a great day!~Caribe Devine

Temperature this Sunday 110 degrees. Perfect time for barbeque. Fire is optional :-)

Moderate temps, college town, huge medical center, within van distance to Scottsdale. And trees.

Well, lowest recorded temperature in Flagstaff was -30 degrees. I am not sure what is worse, Plus 115 degrees in summer in Phoenix, or Minus 30 degrees in winter in Flagstaff, but I would not want to experience either of them.

Both days this weekend the Phoenix temperature is expected to hit 113 degrees, approaching the all time high of 118 degrees for these says. The temperature is expected to be above 110 degrees for the next 6 days at least. But Alcor Boards is happy. Luckily, most of them have to show up at the facility once a year for the annual meeting.

http://www.kswt.com/Global/story.asp?S=10792694&nav=menu613_2_6

Associated Press - July 26, 2009 5:54 PM ET

PHOENIX (AP) - Weather officials have issued an excessive heat warning for the Phoenix metro area and western and southwestern Arizona.

The warning is in effect from 5 p.m. Sunday to 8 p.m. Tuesday, and covers such cities as Yuma, Gila Bend and Wickenburg.

Temperatures are expected to reach 110 to 115 degrees Monday and Tuesday and shouldn't get below the upper 80s at night in many locations.

The higher temperatures are the result of strong high pressure over southern Arizona and the drying out of the moist monsoon air mass that has been in place.

Officials warn people to limit outdoor activities and drink plenty of water.

It has been explained many times that the difference between a summer high in a temperate zone, and a summer high in Phoenix, is trivial compared with the difference between ambient air temperature and liquid nitrogen (-196 C).

Suppose there is a geologically stable location, free from tornadoes and other natural catastrophes, yet well served with amenities such as liquid nitrogen deliveries, in a temperate zone where the summer high never goes above 75 F (i.e. 24 degrees C). I don't think such a place exists in the USA, but, let's pretend.

The difference in temperature between liquid nitrogen and shade temperature in such a temperate zone would be 196 + 24 = 220 degrees.

The typical daytime high, at the peak of the summer in Phoenix, is around 110 (i.e. 43 degrees C).

Therefore the difference in summer-high temperature between the hypothetical temperate zone and Phoenix is 19 degrees.

19/220 = an increase in temperature differential of about 8.5 percent.

I think you have been nattering on about this for--years, is it?--as if 8.5 percent constitutes grounds for accusing Alcor of making a foolish decision to locate itself in Scottsdale. Clearly, other factors are far more important than summer temperature.

How many degrees hotter must it get on an average Phoenix summer day, before increased demands on the electric supply (air conditioners, etc.) start causing brown- and blackouts, shutting down the places that make liquid nitrogen, interrupting transportation that deliver same due to fuel stations closing down, and people no longer being willing to stand the heat so they all get out of the oven, leaving Alcor's suppliers and maybe even Alcor itself devoid of staff? 5 degrees? 10?

It's coming, even if you are a global warming denier (along with other popular things to deny such as the holocaust or the moon landing).

I don't recall, at least in recent years, having ever cited liquid nitrogen boiloff as a serious concern, though I would guess that 8.5% higher temps would create a commensurate increase in boiloff. I have always primarily had the human factors in mind, as to the risk to Alcor's patients from increased overall temperatures.

If they have not already done so secretly in order not to give FD credit for sounding the alarm, Alcor's Board really should give serious consideration to moving the patient storage to a cooler clime.

If they want to keep the rest of Alcor's operations centered in Scottsdale, that would not matter as much, and it could be moved rather quickly and easily should all of Alcor's dedicated employees threaten to move north, Alcor with them or not.

FD

Well, I seem to remember you pouring scorn on the idea of doing cold storage in a hot climate. But, if it's just problems associated with global warming that you are concerned about, bear in mind that global satellite temperature readings have actually declined for the last six or seven years. Chicago has had its coldest June in more than 60 years.

Tucson, meanwhile, is hotter than Phoenix, and so is Las Vegas. Now that the rate of population growth in these western cities has flattened out, I don't see that power generation will be a problem. Other factors such as earthquakes, floods, tornadoes, and hurricanes seem significantly more important.

"...hottest July in Phoenix on record. With an average high temperature of 109.5 degrees ranking second in the city's history and an overall average of 98.3 ranking first, the numbers certainly back up the thought that it was really, really hot. Of course, Phoenicians did not get much of a respite from the heat, as the average low temperature was 87.1 degrees, the highest it has ever been."

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