The latter part of August will be less busy and usually cell service is better. However, cell service depends on your carrier. It is most likely going to be spotty everywhere in the Yosemite area. For weather, we suggest you look at one of these weather sites https://www.accuweather.com/en/us/groveland-ca/95321/august-weather/2143093
Wheater is great
Depends on your cell carrier. Tmobile and AT&T very poor there, Verizon is a little better. We stayed a week I had service outside with Verizon and others had little to no service. We also stayed at the top of the hill. Service was nonexistent at the pool.
We have Verizon and reception worked for us. WiFi didn't work well in our area of the campground. unknown about weather.
Spotty and slow even linked into wi-fi
Weather is likely great. Cell coverage is iffy all year round
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