How to grab first temperature has high and second as low

I need to set high temp for the day as 78 and the low as 60. I am a beginner and would like to know how could i do this in xsl. I was thinking of doing something with the time of day, but not sure. Thanks for your help in advance.

sample code of xml below.

`<forecast>-
<dailyForecastPeriods>
<temperature>78</temperature><forecastDateLocalStr>2014-07-18T07:00:00</forecastDateLocalStr><forecastDateUtcStr>2014-07-18T11:00:00Z</forecastDateUtcStr><isNightTimePeriod>false</isNightTimePeriod>
</dailyForecastPeriods>
-<dailyForecastPeriods>
<temperature>60</temperature><forecastDateLocalStr>2014-07-18T19:00:00</forecastDateLocalStr><forecastDateUtcStr>2014-07-18T23:00:00Z</forecastDateUtcStr><isNightTimePeriod>true</isNightTimePeriod>`

Sample of xsl
`<tr>
<xsl:for-each select="//forecast/dailyForecastPeriods">
    <xsl:if test="position() > $startIndex">
    <xsl:if test="position() &lt;= ($numDays)+$startIndex">
    <td title="{detailedDescription}" align="center"
valign="top"class="weatherforecasttemp">
     <span class="weatherforecasthigh">
     <xsl:value-of select="temperature"/>
         <xsl:text>°</xsl:text>                     
     </span>
      <xsl:text>&#160;</xsl:text>
      <span class="weatherforecastlow">
      <xsl:value-of select="temperature" />
      <xsl:text>°</xsl:text>
               </span>
               </td>
              </xsl:if>
              </xsl:if>
              </xsl:for-each>
            </tr>`