Answer: As long as they are watered properly (to a depth of about 2 feet), palms thrive in the heat. Palm trees are susceptible to nitrogen, potassium, and magnesium nutrient deficiencies, which may show up as yellowing, and they also need various micronutrients. I recommend you use a fertilizer formulated especially for palms. According to University of Arizona experts, it should have 10-20% Nitrogen and Phosphorus, 5% Potassium and 1-3% Mg, .5% Mn, .5% Fe, as well as trace amounts of S, Zn, Cu and B. This will be on the package label. Follow instructions exactly for amounts and water well after application.
You can download a free publication on palm care from the University of Arizona Cooperative Extension at the following site:
Click on Ornamentals and then Palms, AZ1021.
Finally, note that sago palms are not true palms, but cycads. They don't take full sun, preferring partial sun to full shade, so if yours is in full sun, that could be the cause of the yellowing.
Q&A Library Searching Tips