Agree you need to start with your vet to understand what and what time of year certain conditions are right to pose the greatest risk of infection in your area. There can be differences if you're coastal or inland as well. Some shots are only needed to be boostered once a year while others only offer protection for 2-6 months.
Eastern and Western equine encephalomyelitis and tetanus (toxoid) only need to be administered once a year for the majority of the US (some deep southern regions might benefit from semi annual EWEE) Spring vaccinations are most desirable as the vector for the EE diseases are mosquitoes and you will provide the most protection in the height of the season. WNV is again more prevalent in the summer months and the vaccine is good for about 4-5 months. If you hold off until April/May, you can get through September with only one booster. A waste of $$ to give WN going into winter. Flu is more prevalent in the fall and most are going to offer the best protect for only 6 months. Rhino can be an issue all year depending upon your herd structure, showing and traveling but the vaccine is only good for 2-3 months.