4. Hot dry weather:

Apply for the months having an average mean maximum temperature of 65 degrees or more, with 6 or less days of .01 inch or over of precipitation. Deficiency to be based on m t2

Average number of days per month with 0.01 inch precipitation.

5. Unusual or exceptional conditions. Apply for conditions not measurable by the climatic conditions above, which offset protection and increase the probability of starting fires: These to include frequency and extent of forest fires which might extend into the city; tornadoes, hurricanes and cyclones which result in numerous fires or interruption of fire service; blizzards and severe snow storms which impede operation of the fire department; earthquakes of such intensities as to injure buildings, water mains and cause numerous fires; mine cave-ins affecting extensive areas, and floods which cover part of the district considered or cause wide detours of fire apparatus.

On the basis of numbers; one each 10 years shall be classed as seriously frequent, and one each 20 years moderately frequent; the extent or effect of the conditions shall increase or decrease this proportionately.

Use 1 times Deficiency Scale.

Difference in grading of water supply and fire department.-Where the fractional classes corresponding to the points of deficiency of the water supply and fire department, that is, the points of deficiency divided respectively by 170 and 150, differ by 3 classes or more, there shall be added to the total points of deficiency a certain number of points varying with the amount of divergence between the classes of the two features. The number of points to be added shall be determined by the following table, proportioning for fractional divergence in classes: