Page is the closest town to The Wave with a reporting weather station at the Airport (KPGA). Elevation at the weather station is 4,308 feet which is about 900 feet lower than that of The Wave. Temperatures at The Wave should run about four degrees cooler than those in Page. Clicking on the image below will provide more details including radar and a forecast.
There is a "personal" weather station (PWS) closer to The Wave on the southwest part of Vermillion Cliffs NM. The PWS is on the cliffs about ten miles North of 89A. Current and historical data at this station is available here. This station is owned by the BLM and reported data seems to be reliable. Elevation is reported at 6,556 feet so temperatures will average about five degrees colder than those at the Wave.
It is "relatively" easy to get permits in January and early February, especially through the walk in process. However there is a good chance there will be snow on the ground in these months. Snow makes hiking difficult and photographing the patterns in the red rock chancy. If there is snow you may be limited to shooting southern exposures such as Fatali's Boneyard and Sand Cove. Average cloud cover is also high in the winter months, and House Rock Road is often muddy and difficult or impossible to drive on. The South Buttes are even higher in elevation than the Wave, about 6,200 feet, or four degrees cooler. This makes snow even more likely in the South Buttes, and it will last longer. I have been to Cottonwood Cove when the north facing exposures had over a foot of snow on them.
These are good months to visit, especially April and May when cloud cover is low and temperatures moderate. Permits are difficult. Average wind speed is highest in the Southwest in the Spring. The wind comes from the Southwest in this area all year round peaking in the afternoon. Sand Cove runs North - South and forms a natural wind tunnel. This makes good photography of Sand Cove and Fatali's Boneyard difficult in the Spring. Average cloud cover is low during May.
A very good month to go to The Wave if you don't mind the heat. Cloud cover is low as is precipitation. The best month for night photography as the Milky Way stretches across the sky.
I used to believe these were the worst months to go to the Wave. I now believe they are reasonably good, if you are prepared and can stand the heat. Average daily high temperature at the Wave is 101 ºF in July and there is little shade. If you go in July do not plan to be out all day. Either go in the morning when temperatures and cloud cover are lower, or go in mid afternoon if the weather looks cooperative. In 2013 there were three heat related fatalities at the Wave, so go prepared. If you plan to stay the whole day you will need to find shade. A space blanket can help, try to find a way to elevate it with hiking sticks, rocks, bushes, ... A good place to find natural shade is on Toprock at the Alcove. Finally bring at least one gallon of water per person in July and August. You will need it. I have seen recommendations of nine liters per person per day when temperatures are this high! There is a good possibility of afternoon thunderstorms or even hail. Mornings are cooler, often clear, and have little wind. It's likely you can get a good photograph in the morning, and if the weather cooperates you may get a great one in the afternoon! With luck there will be water at the Wave or in the water pockets south of The Wave. Water pockets won't last long given the average July August temperatures though. If there are water pockets look for tadpoles and tadpole shrimp. If there's a lot of water you may even hear toads croaking! (males calling for females). Permits, though still difficult, are much easier to get than during the peak months.
Excellent months for visiting, Page and Kanab are less crowded than during summer vacation, and cloud cover and temperatures are reasonable. Permits are very difficult to get. The rest of the Southwest is also beautiful at this time of year with the Aspens changing in late September/early October, and the Cottonwoods in late October.
The following table was constructed using ten years of daily data from the Page weather station:
Wind Speed MPH
An Excel file containing Page daily weather data for the last ten years can be downloaded by double clicking on the image below:
Another good source of climate information based on the Page Airport data can be found at Weatherspark.com.