for weather for both climbs , i usually check the wrightwood temps and big bear lake temps and average both.

dawson saddle...the second link is the one. higher/longer. bragging rights. it is paved the entire way. the elevation becomes a factor.
a lot of cold air sink in that canyon in the morning but it can heat up a lot on the ascent until you get to the crystal lake
turnoff and essentially escape from the canyon.
the 4.5-5 mile stretch between the crystal lake turnoff along hwy 39 and the 39/2 junction is gated-so go around, over or through
the gate on both ends. on that 4.5-5 mile "closed" stretch, there will be rockfall on the road. not a problem on the ascent but
pay attention on the descent. there may or may not be caltrans snow/rockplow trucks working that stretch while you're up there.
there is water available along hwy 39 but i haven't had any luck in the campgrounds or turnouts along the way during a few, cursory
investigations. the crystal lake store (if open-check for hours) has supplies. there is also an active stream about 2 miles uphill (north)
of the east fork junction (11 miles up?) on your right side during the ascent. fast flowing stream close and relatively accessible from the 39.
i wouldn't drink any untreated/unfiltered water from the stream but it is a great place to douse your cycling cap/bandana/ jersey/underlayer
if it is hot. there is a spring on the side of the highway approx 5 miles uphill that is another good spot to soak yourself if necessary. once past
the crystal lake turnoff, there's no water available. very long climb (along with the onyx summit climb in the neighboring san bernardino mtns)
but worth it. the first 16 miles are relatively easy; the second 16 miles add the elevation along with a steeper grade.

for the mt. baldy approach, both are good but the first segment (gmr/grr-4457315) is the one. epic. arguably the best cycling climb in socal period.
scenic. challenging. exposed. you are climbing along the edge or top of the canyon the entire way until mt. baldy village. no supplies/phone reception
for 20 miles. the long dawson saddle climb is essential but this one stirs the soul.
if you only had one last climb to do in socal, this would be the one. no supplies or water sources between the bottom of the climb and mt. baldy village.
save something for the last few miles on the ascent from mt. baldy village to the ski lifts because it is brutal. the descent back to the village is unpleasant
because of the steep switchbacks and the pavement quality.

one word for both ascents...weekday. enjoy.