I've only lost one bird to heat. It was a Welsummer in that terrible summer we had a couple years ago.The site is:
http://www.weather.com/weather/wxclimatology/monthly/graph/USMO0460
Woodland is close to the break between the Coast Range Mountains and the Santa Cruz Mountains. We actually get an off shore Ocean wind for a lot of the Summer called the Delta Breeze. The lows you see are because of that Breeze. North of us and south of us does not get that so the record and average temperatures are higher.
I grew up in Red Bluff California and the Record high for Red Bluff does not fit on the Chart! 121.9 in 1976! The chart says 121 but drops it below the 119 that fits.
I lived there then and it was terrible. We had 7 of our chickens blow up....Quite sad.
I've never lost one to cold.
Ron, I hope the weather shifts and you guys finally get some real precipitation.
That shift would probably give us some warmer weather too.