One of the mildest San Francisco Augusts in 143 years

Temperature records in San Francisco began in 1874 and this August will tie as only the 4th time that there was not a daily maximum temperature all month that did not exceed 70 degrees. In 1942 the highest reading for the month was only 67 degrees, while in 1917 and 1882 the highest was 69. On August 8, 2016 the maximum was just 70 degrees, tying it with 1881.

So far in August 2016 the average maximum temperature has been 64.6, and given forecast maxima of around 64 degrees for the remainder of the month this will change little. The normal August high temperature in San Francisco is 68.1. But even with prolonged coolness, the average for the month will only rank as about the 35th coolest on record.

The major player in the mild weather has been a persistent weak trough of low pressure over the West Coast for most of the month and a likewise persistent marine layer.  It should be noted that the sea surface temperatures along the coast west of San Francisco remained above normal for the entire month.

The story is different farther inland and away from the cool coastal air with August monthly maximums generally above normal.

Finally I would be remiss if I did not point out that Mark Twain NEVER SAID "the coldest winter I ever spent was summer in San Francicsco". (per  But if he had, it would likely have been a year like 2016.

Jan Null, CCM
Golden Gate Weather Services



Confusing 5-minute Weather Observations

Caveat Emptor.

Some NOAA websites are beginning to display ASOS (i.e., airport weather) observations every 5-minutes.  An example is  While at first blush this seems like an awesome way to see more timely data, it can cause confusion when comparing it to daily maximum and minimum readings.

Example of 5-minute readings:

The 5-minute readings are actually an "instantaneous" 1-minute observation at the particular time noted. The problem arises in that the maxima and minima are a "5-minute average" of five adjacent individual 1-minute readings.  Consequently, that average could be less than one of the 5-minute readings.

For example, at the hottest time of the day you have an instantaneous 5-minute reading of 85 degrees at 14:30.  However, if the readings at 14:27, 14:28, 14:29 and 14:31 were all 84 degrees, then the maximum reading would be 84.2, which would be rounded to 84.

Correction: In rereading the ASOS criteria I think I misinterpreted how’s it’s calculated (i.e., the 5-min values are the average of the previous five 1-min values) and that rounding due to C to F conversions may be more of a factor.  But overall I am right for the wrong reasons and for the real world the confusion remains with seeing different 5-min values than the climatological max/min temps.

Jan Null, CCM
Golden Gate Weather Services



End of the 2015-16 Rainfall Season

Today is the last day of 2015-16 California rainfall season and it certainly has been an interesting one.  Going into the season with El Niño developing in the Pacific, I don't know anyone who envisioned that Northern California would have seen a significantly greater percent of normal amounts than Southern California; once again highlighting that 2015-16 was the Poster Child for "All El Niños Are Not the Same".

The map and table below an also be found at

The following map was generated from the Western Region Climate Center

Jan Null, CCM
Golden Gate Weather Services



Is a "Different" La Niña Brewing?

Are the impacts, from the La Niña that is forecast to develop later this year, going to be "typical" or will they be more of an outlier solution like that of the fading El Niño? (Differences Between 2015-16 El Niño and Previous Strong and Very Strong  Events)  

A comparison of the current NASA Sea Surface Height anomalies and those in May 1998 show some reason to keep an open mind. Note the large positive anomaly north of the equator; which is the same mass that was at least partially responsible for the 2015-16 El Niño being atypical.

And this area is literally outside of the Niño 3.4 box where SST anomalies are measured and used to gauge the presence and strength of ENSO events. Consequently, while the Oceanic Niño Index (ONI) may be showing cooling, this area will need to be watched as well.

In that context, even La Niña - Anything Goes for California Precipitation may not give enough clues for this coming winter. As always, it will be interesting and challenging. Stay tuned.

Jan Null, CCM
Golden Gate Weather Services


Updated Golden Gate Weather Services Web Resources

The following pages have been updated.  As always, let me know of any changes, corrections or additions.

2016 Thunderstorm & Tornado Resources

2016 Hurricane Resources 

2016 Fire Weather Forecasts and Links 

El Niño/La Niña Resources

Heatstroke Deaths of Children in Vehicles

All of the above, and much more, can be accessed from the Meteorologist's Links page. 

Blog: Most of these emails and other material get archived in the Golden Gate Weather Services Blog.

Twitter:  Short updates and links send more frequently via @ggweather 

Jan Null, CCM
Golden Gate Weather Services



La Niña - Anything Goes for California Precipitation

In looking at past La Niña events, the one thing that is clear is that almost anything can happen when it comes to winter precipitation across the Golden State.  The images below show the "average" precipitation for the 20 previous La Niña events going back to 1950 but more importantly the wide range from the driest to the wettest California winters (Nov. - Mar.) for each of the categories (Weak, Moderate and Strong).  [Additional images and data can be found at US Winter Precipitation & Temperature Climatology: La Niña and California Climatology of La Niña Events and Precipitation]


The bottom line is that it is too early to tell the strength of forecast La Niña and more importantly even within a specific strength category the range of solutions leaves no clear signal based on the past climatology.

Jan Null, CCM
Golden Gate Weather Services


Northern Sierra Precipitation Tops Seasonal Normal

The 8-Station northern Sierra Nevada (see map) precipitation Index (8SI) has reached a milestone. Rain and snow over the weekend pushed its total since July 1st to 55.71". This is over an inch above normal for the entire seasonal (July 1 to Jun 30) total of 54.52”.  Normal 8SI for the remainder of April plus May and June is approximately an additional 4 inches.

The 5-station San Joaquin Basin Index is now at 39.71" compared to their seasonal total of 42.57" and the 6-station Tulare Basin Index is at 26.00" compared to their full season normal of 30.50".

Jan Null, CCM
Golden Gate Weather Services

Note: There will be a minor discrepancies between these figures and those published by Calif. DWR which uses the Oct. 1 Water Year instead of the historical rainfall season of July 1 to June 30.  And inexplicably DWR also does not use the standard 30-year climatological normal (1981-2010) but rather non-standard average period of 1922-1998 for the 8-Station Index (50.00") and 1961-2010 for the 5 and 6-Station Indices.   




Precious Cargo

As the temperatures begin to go up, sadly so do the number of children who die after being left inside hot vehicles.  Already in 2016 there has been the two such deaths nationwide.  And it does not have to be a blazing hot day in a southern state for these tragedies to take place as evidenced by the fact of deaths in places like Seattle and Milwaukee on mild days. 

We have all heard about an isolated incident of a child dying in a hot car.  However when put into a nationwide context they constitute an epidemic; claiming on average 37 young lives every year in the United States.  Since 1998 over 662 infants and children have died horrible deaths due to heatstroke inside hot vehicles.  But you can help save some of these precious lives!

Sadly, these incidents often intersect with the early childhood education and childcare communities.  Over half (54%) of juvenile vehicular hyperthermia fatalities occur when a caregiver is somehow distracted and accidentally leaves a child in a vehicle.  And in nearly half of these cases, the child was supposed to be dropped off at either childcare or preschool.  These cases happen to parents, grandparents, siblings and childcare providers.  It is often a matter of a change of routine, where one person normally is responsible for a child and on a given day another person forgets they have the responsibility that day.

The other categories of circumstances that lead to heatstroke deaths in vehicles are children playing in vehicles and children intentionally left in vehicles.  In the former, which account for about 29% of the cases, children gain access to a vehicle and are subsequently overcome by the heat.  And sadly in the latter instance that makes up about one-in-five of the deaths (17%), children are intentionally left in vehicles by a caregiver who has to run an errand, go to work, go to bar or the casino, etcetera.

What is heatstroke (aka hyperthermia)?  In the simplest terms it describes heat-related illnesses when a body’s temperature exceeds its normal range.  If a body is subjected to extreme temperatures it can overwhelm the body’s ability to cool itself.  This is especially true for infants and children whose body’s heat at a rate of three to five times faster than adult.  If a person’s body temperature reaches 104 degrees (the clinical definition for heat stroke) their cooling system is overwhelmed to the point it begins to shut down.  A person with heat stroke may experience symptoms that include confusion, faintness, strong and rapid pulse, and possible delirium, hot dry skin or even unconsciousness.  Continued exposure to very high temperatures can produce brain damage, and at 107 degrees cells with the body start to die and organs begin to shut down, quickly leading to death.

In the summer of 2002 a controlled study was conducted to quantify how hot vehicles get and how rapidly they can reach dangerous temperatures.  This research was published in Pediatrics and is maintained on line at  The conclusions of the research were startling in how extreme the conditions inside a car can reach.  Within the first 10 minutes a vehicle will warm to almost 20 degrees above the outside air temperature; after 30 minutes it is 34 degrees warmer. After an hour it plateaus at as much as 45 to 55 degrees higher than the air outside.  Consequently, even on a mild 70 degree day temperatures can reach readings that can be fatal to an infant or small child.  The research also found that “cracking” the windows had a negligible effect on the temperature.

This research has become the “go to” article on the topic and is used worldwide and hopefully will raise the level of interest and awareness about this sad topic and ultimately to save some innocent lives.  The bottom line is that each and every one of these deaths is 100% preventable.  Infants and children are the most precious cargo that is ever transported in a vehicle and we should always be cognizant of the potential dangers to a child left alone in a car.

Jan Null, CCM
San Jose State University


Safety Recommendations

• Be sure that all occupants leave the vehicle when unloading. Don't overlook sleeping babies.
• Always lock your car and ensure children do not have access to keys or remote entry devices.  If a child is missing, check the pool first and then the car, including the trunk. Teach your children that vehicles are never to be used as a play area.
• Keep a stuffed animal in the carseat and when the child is put in the seat place the animal in the front with the driver.
• Or place your purse or briefcase in the back seat as a reminder that you have your child in the car.
• Make "look before you leave" a routine whenever you get out of the car.



March and Season-to Date Rainfall summary

March rainfall across California was somewhat reflective of the season-to-date with above normal totals farther north in the state. 


These numbers continue to tell the story that this El Niño was "different". (See

Jan Null, CCM
Golden Gate Weather Services 

Note: There will be a minor discrepancies between these figures and those published by Calif. DWR and some NWS offices which uses the Oct. 1 Water Year instead of the historical rainfall season of July 1 to June 30. DWR also does not use the standard 30-year climatological normal (1981-2010) but rather non-standard average period of 1922-1998 for the 8-Station Index and 1961-2010 for the 5 and 6-Station Indices.