High pressure strength will peak Friday limiting any marine influence in the deep interior valleys of SLO county. This should produce temps of 102-105 across the SLO county interior. 107 is Friday’s record for Paso Robles and 89 is an average daily high this time of year.
Today is the first day of summer the solstice having occurred at 3:07 am with 14 hours-29 minutes of daylight. Solstice is the highest the sun gets in the sky, days actually get shorter from here until the fall equinox.
The coastal weather is dramatically different than the interior. In fact high temps could differ by 45 degrees Friday with places like Morro Bay probably only seeing a high temperature around 60. The marine layer is pinned down by a strong inversion and afternoon NW winds will act to push the cooler air into the coastal valleys helping places like SLO and Santa Maria not get very hot, temps should be near their seasonal average.
I think Saturday will still be quite hot inland but perhaps a few degrees cooler, still topping 100. Sunday we’ll see some good cooling inland, with my forecast high temps around 90. The ridge weakens but a flat-zonal jet stream pattern in the extended forecast should produce a number of days with highs in the low to mid 90s. Coastal highs look very steady between now and the end of the month.