The weather in San Diego is normally gorgeous. Temperatures inland will normally vary from a afternoon high in the low 100's in August to a 2 A.M. low in the 30's in January. Humidity is generally low and it seldom rains. (Escondido typically gets 10 inches of rain each year) Add to that great mountain roads, scenic desert, and a beautiful coastline and you have great motorcycling.
The San Diego Area consists of four different regions: Coastal, Inland, Mountain, and Desert. If you check the weather, you will find a different forecast for each region. The Pacific Ocean stabilizes the weather such that there is a narrower range of temperatures near the coast. Likewise, there is a wider range of temperatures as you get farther inland. You will experience higher humidity near the coast than inland but San Diego is relatively arid year round.
You will typically experience a temperature swing of up to 30 degrees F in a day depending how far you are from the ocean. For example, Escondido (Inland Region) may have a high of 75 at 2 P.M. and a low of 45 degrees at 2 A.M. Depending upon the season, this range of temperatures shifts the best times for riding.
The hottest weather occurs from mid-July thru early October where the inland temperatures will typically hit a high in the upper 90's. During these months, we tend to ride late afternoon and early evening while staying closer to the coast. During summer months, desert temperatures will get up to 120 degrees or more. At the higher mountain altitudes, you can expect to encounter snow and ice during winter months. We have had some rides where we have passed thru all four seasons!
Ocassionally, San Diego will experience Santa Ana conditions where the wind blows from East to West rather than the normal direction of West to East. This will cause January temperatures in the 70's and 80's sharply contrasting with the rest of the county. This will also cause our summer high temperatures to reach the 100's inland. A Santa Ana will also bring strong and very dry winds.
Almost every day is sunny in San Diego and the sunlight can be intense. Dark sun glasses are highly advised when riding and sun screen is sometimes needed. You should use special care when riding from bright sunlight into shadows and allow your eyes to adjust. Most rides end by heading West late in the day and you may find yourself blinded by the sun. San Diego does have spectacular sunsets over the ocean.
The San Diego area typically gets 10 inches of rain each year. Much of this rain will fall overnight. Some of our recent years have been below average drought years with perhaps 4 inches of rain each year. This caused the water level of many of the reservoirs to drop far below normal. Other years, the opposite was true as San Diego has experienced El Nino rainfall. Overall, it is unlikely that you will need a rain suit when riding in San Diego.
The dry climate means that there are few bugs -- essentially no mosquitoes. You can sit outside for hours in the evening without being bothered. It is especially nice to dine outdoors. Flowers bloom essentially year round so there are a lot of honey bees. It is advisable to have a windshield or similar protection to avoid taking a bee hit.
San Diego has a wide variety of animal life. It's always fun to see a road runner or coyote dash across the road as long as you maintain control of your bike. We have had several times in the early spring when we have quickly passed a rattlesnake sunning itself on an obscure back road. It happens so quickly that you have to look back to see what you just passed. If you are lucky you can see an eagle or big horn sheep. You can expect to see lots of hawks.
San Diego area roads tend to be very good quality due to the reduced temperature range. It should be rare that you encounter pot holes. The roads are usually clear of gravel and rocks but it pays to be watchful, especially in the mountains. Watch for fallen fruit on the road when passing orchards.
Many of our mountain roads are very popular with sport bikers who love to race. If you are riding a cruiser, be prepared to be passed at any time and watch for on-coming bikes.