RESULTS 

 Weather Factors 



The two "fire seasons" differed quite drastically in terms of temperature, humidity, 

 and precipitation trends. Perhaps the most striking difference was in quantity 

 and distribution of precipitation (fig. 3). The main difference between humidity 

 patterns for 1968 and 1969 occurred after August 1. During 1968, the average humidities 

 at 1630 hours were around 40 percent or higher throughout August and September. However, 

 during 1969 humidities averaged 20 percent and did not rise above 30 percent until 

 mid- September . Temperatures during the same period averaged about 20° higher in 1969. 



The National Fire-Danger Rating Buildup Index, which accumulates daily drying 

 conditions by integrating temperature, humidity, and rainfall, was plotted for 1968 and 

 1969 (fig. 4). On August 12 of both years the index had reached 200 or above. The 

 index dropped to below 25 on August 13, 1968, and remained below 50 for the rest of the 

 summer. In 1969 the index kept climbing until it reached 380 on September 18, at which 

 time it dropped due to the first fall rains. These weather data show that the months 

 of August and most of September were wet and cool in 1968 and dry and hot in 1969. 



o 

 o 

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"u 



JUNE 



JULY 



AUGUST 



SEPT 



OCTOBER 



Figure 3. — Ifie aooumulated preaipitation during the 1968 and 



1969 fire seasons. 



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