diff --git a/NEWS.md b/NEWS.md
index 1860e00..54ba739 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,6 +4,8 @@
 - Improved messages regarding what date/time ranges are being queried and returned by data retrieval functions.
 - `az_hourly()` now returns data from the previous hour when `start_date_time` and `end_date_time` are not supplied rather than returning the previous day of hourly data.
 - `azmet` is now much more verbose, printing messages about which data are requested and which data are returned.
+- Added an option `"azmet.print_api_call"` which, when set to `TRUE` prints the HTTP request sent to the API—for debugging purposes.
+- Fixed a bug that caused an error when data was requested from all stations but some stations didn't have data for all variables.
 - Requests for data before January 1, 2021 now error, since these data are not on the AZMet API (yet).
 
 # azmetr 0.2.1
diff --git a/R/az_heat.R b/R/az_heat.R
index a66a12d..dcb077b 100644
--- a/R/az_heat.R
+++ b/R/az_heat.R
@@ -64,6 +64,12 @@ az_heat <- function(station_id = NULL, start_date = NULL, end_date = NULL) {
     }
   }
   params <- parse_params(station_id, start = start_date, end = end_date)
+  # always add a day to time_interval for heat endpoint to match how API works
+  if (params$time_interval != "*") {
+    params$time_interval <-
+      lubridate::format_ISO8601(lubridate::as.period(params$time_interval) +
+                                  lubridate::days(1))
+  }
 
   # Query API --------------------------------------------
 
@@ -112,9 +118,8 @@ az_heat <- function(station_id = NULL, start_date = NULL, end_date = NULL) {
           dplyr::if_else(x %in% c(-999, -9999, -99999, -7999, 999, 999.9, 9999), NA_real_, x))
     )
 
-  # Since output from API doesn't contain any information about dates, this is just an assumption
   message("Returning data from ", format(params$start, "%Y-%m-%d"),
-          " through ", format(params$end, "%Y-%m-%d"))
+          " through ", format(max(out$datetime_last), "%Y-%m-%d"))
 
   return(out)
 }
diff --git a/R/retrieve_data.R b/R/retrieve_data.R
index 0efc0b0..530f30e 100644
--- a/R/retrieve_data.R
+++ b/R/retrieve_data.R
@@ -4,12 +4,14 @@
 #' @param start_f character; ISO formatted date time string
 #' @param time_interval character; ISO8601 formatted time interval string
 #' @param endpoint character; one of "daily", "hourly", or "hueto"
+#' @param print_call logical; when TRUE, prints the HTTP request to the AZMet API
 #'
 #' @return tibble
 #' @noRd
 #'
 retrieve_data <- function(station_id, start_f, time_interval,
-                          endpoint = c("daily", "hourly", "hueto")) {
+                          endpoint = c("daily", "hourly", "hueto"),
+                          print_call = getOption("azmet.print_api_call")) {
   endpoint <- match.arg(endpoint)
 
   req <- httr2::request(base_url) %>%
@@ -19,6 +21,10 @@ retrieve_data <- function(station_id, start_f, time_interval,
     #limit rate to 4 calls per second
     httr2::req_throttle(4 / 1)
 
+  if (isTRUE(print_call)) {
+    print(req)
+  }
+
   resp <- req %>%
     httr2::req_perform()
 
@@ -29,7 +35,10 @@ retrieve_data <- function(station_id, start_f, time_interval,
   }
 
   data_tidy <- data_raw$data %>%
-    purrr::map_df(tibble::as_tibble)
+    purrr::compact() %>%
+    purrr::map(purrr::compact) %>% #removes any columns that are NULL (i.e. no data)
+    purrr::map(tibble::as_tibble) %>%
+    purrr::list_rbind() # missing columns for individual sites will be all NAs
 
   attributes(data_tidy) <-
     append(attributes(data_tidy), list(
diff --git a/tests/testthat/test-az_heat.R b/tests/testthat/test-az_heat.R
index e834a2c..9eac87e 100644
--- a/tests/testthat/test-az_heat.R
+++ b/tests/testthat/test-az_heat.R
@@ -17,6 +17,28 @@ test_that("az_heat() returns only one row per station even with dates", {
   expect_equal(nrow(res_start), 1)
 })
 
+test_that("start and end dates interpreted correctly", {
+  res <- az_heat(station_id = 1, start_date = "2023-10-10", end_date = "2023-10-30")
+
+  expect_equal(res$datetime_last, lubridate::ymd("2023-10-30"))
+
+
+  skip("not sure of desired behavior")
+  expect_error(az_heat(station_id = 1, end_date = "2022-09-01"), "`end_date` is before `start_date`!")
+})
+
+test_that("end_date can be specified without start_date", {
+  yesterday <- lubridate::today() - lubridate::days(1)
+  res_end_old <- az_heat(station_id = 1, end_date = "2022-09-27")
+  res_end_yesterday <- az_heat(station_id = 2, end_date = yesterday)
+
+  expect_s3_class(res_end_yesterday, "data.frame")
+  expect_equal(res_end_yesterday$datetime_last, yesterday)
+
+  skip("not sure of desired behavior here")
+  expect_equal(res_end_old$datetime_last, lubridate::ymd("2022-09-27"))
+})
+
 test_that("works with station_id as a vector", {
   res_2 <- az_heat(station_id = c(1, 2))
 
@@ -67,13 +89,16 @@ test_that("start_date = NULL, end_date specified works", {
     az_heat(station_id = 1, end_date = yesterday),
     glue::glue("Returning data from {lubridate::floor_date(yesterday, 'year')} through {yesterday}")
   )
+  expect_s3_class(
+    az_heat(end_date = "2022-02-01"),
+    "tbl_df"
+  )
   expect_message(
-    az_heat(station_id = 1, end_date = "2022-02-01"),
+    az_heat(end_date = "2022-02-01"),
     "Returning data from 2022-01-01 through 2022-02-01"
   )
 })
 
-
 test_that("start_date specified, end_date=NULL works", {
   yesterday <- lubridate::today(tzone = "America/Phoenix") - 1
   last_month <- yesterday - lubridate::days(30)