diff --git a/pkg/cache/cache.go b/pkg/cache/cache.go
index 6bfbda0..9b908bf 100644
--- a/pkg/cache/cache.go
+++ b/pkg/cache/cache.go
@@ -23,22 +23,32 @@ func New[T any](path string) *Cache[T] {
 	return &Cache[T]{path}
 }
 
+var (
+	ErrorUnableToMarshalJSON        = errors.New("unable to marshal as JSON")
+	ErrorUnableToEnsureCacheDir     = errors.New("unable to ensure cache-dir is present")
+	ErrorUnableToWriteCache         = errors.New("unable to write data to cache file")
+	ErrorUnableToOpenCacheFile      = errors.New("unable to open cache")
+	ErrorUnableToReadCacheFile      = errors.New("unable to read cache")
+	ErrorUnableToUnmarshalCacheFile = errors.New("unable to unmarshal JSON from cache-file")
+	ErrorUnableToReadCachePath      = errors.New("unable to read from cache path")
+)
+
 // Add data as JSON-file into cache-dir, returns nil if success
 func (c *Cache[T]) Add(name string, data any) error {
 	j, err := json.MarshalIndent(data, "", " ")
 	if err != nil {
-		return fmt.Errorf("Failed to convert data as JSON.")
+		return ErrorUnableToMarshalJSON
 	}
 	err = os.MkdirAll(c.Path, 0646)
 	if err != nil {
-		return fmt.Errorf("Failed to ensure cache-dir is present.")
+		return ErrorUnableToEnsureCacheDir
 	}
 
 	filePath := filepath.Join(c.Path, filename(name))
 	d := []byte(j)
 	err = os.WriteFile(filePath, d, 0646)
 	if err != nil {
-		return fmt.Errorf("Failed write data to cache-file.")
+		return ErrorUnableToWriteCache
 	}
 
 	return nil
@@ -53,19 +63,19 @@ func (c *Cache[T]) Get(name string) (*T, error) {
 
 	rawFile, err := os.Open(filePath)
 	if err != nil {
-		return nil, fmt.Errorf("Failed to read cache-file.")
+		return nil, ErrorUnableToOpenCacheFile
 	}
 
 	var result T
 
 	bytes, err := io.ReadAll(rawFile)
 	if err != nil {
-		return nil, fmt.Errorf("Failed to read data from cache-file.")
+		return nil, ErrorUnableToReadCacheFile
 	}
 
 	err = json.Unmarshal(bytes, &result)
 	if err != nil {
-		return nil, fmt.Errorf("Failed to parse JSON from cache-file.")
+		return nil, ErrorUnableToUnmarshalCacheFile
 	}
 
 	return &result, nil
@@ -80,7 +90,7 @@ func (c *Cache[T]) List() ([]Saved[T], error) {
 	var result []Saved[T]
 	filenames, err := list(c.Path)
 	if err != nil {
-		return nil, fmt.Errorf("Unable to read from cache path")
+		return nil, ErrorUnableToReadCachePath
 	}
 
 	if len(filenames) == 0 {
@@ -102,7 +112,7 @@ func (c *Cache[T]) List() ([]Saved[T], error) {
 func list(path string) ([]string, error) {
 	dir, err := os.ReadDir(path)
 	if err != nil {
-		return nil, fmt.Errorf("Unable to read from path")
+		return nil, ErrorUnableToReadCachePath
 	}
 	var filenames []string
 
diff --git a/pkg/met/met.go b/pkg/met/met.go
index ed9076a..02a03fa 100644
--- a/pkg/met/met.go
+++ b/pkg/met/met.go
@@ -3,6 +3,7 @@ package met
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -13,10 +14,18 @@ type Met struct {
 	siteName string
 }
 
+var (
+	ErrorMissingSiteName           = errors.New("siteName must be defined")
+	ErrorMissingHeaderExpires      = errors.New("missing header 'Expires'")
+	ErrorMissingHeaderLastModified = errors.New("missing header 'Last-Modified'")
+	ErrorParseExpires              = errors.New("unable to parse 'Expires'")
+	ErrorParseLastModified         = errors.New("unable to parse 'Last-Modified'")
+)
+
 // Returns valid Met client or error if empty siteName is provided
 func New(siteName string) (*Met, error) {
 	if siteName == "" {
-		return nil, fmt.Errorf("`siteName` must be defined.")
+		return nil, ErrorMissingSiteName
 	}
 
 	return &Met{
@@ -60,19 +69,19 @@ func (m *Met) Forecast(lat, lon float64, alt *int) (*LocationForecastResult, err
 
 	expiresRaw, ok := resp.Header["Expires"]
 	if !ok {
-		return nil, fmt.Errorf("Unable to get 'Expires' header")
+		return nil, ErrorMissingHeaderExpires
 	}
 	expires, err := time.Parse(time.RFC1123, expiresRaw[0])
 	if err != nil {
-		return nil, fmt.Errorf("Unable to parse `expiresRaw`: %w", err)
+		return nil, errors.Join(ErrorParseExpires, err)
 	}
 	lastModifiedRaw, ok := resp.Header["Last-Modified"]
 	if !ok {
-		return nil, fmt.Errorf("Unable to get 'Last-Modified' header")
+		return nil, ErrorMissingHeaderLastModified
 	}
 	lastModified, err := time.Parse(time.RFC1123, lastModifiedRaw[0])
 	if err != nil {
-		return nil, fmt.Errorf("Unable to parse `Last-Modified`: %w", err)
+		return nil, errors.Join(ErrorParseLastModified, err)
 	}
 
 	forecast := LocationForecast{}
diff --git a/pkg/nominatim/nominatim.go b/pkg/nominatim/nominatim.go
index 8fd126c..fb40a9c 100644
--- a/pkg/nominatim/nominatim.go
+++ b/pkg/nominatim/nominatim.go
@@ -2,6 +2,7 @@ package nominatim
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -14,9 +15,13 @@ type Nominatim struct {
 	siteName string
 }
 
+var (
+	ErrorMissingSiteName = errors.New("siteName must be defined")
+)
+
 func New(siteName string) (*Nominatim, error) {
 	if siteName == "" {
-		return nil, fmt.Errorf("`siteName` must be defined.")
+		return nil, ErrorMissingSiteName
 	}
 
 	return &Nominatim{
@@ -94,7 +99,7 @@ func (n *Nominatim) Reverse(lat, lon float64) (*ReverseResult, error) {
 	}
 
 	if allFieldsNil(result) {
-		return nil, fmt.Errorf("No result")
+		return nil, fmt.Errorf("no result")
 	}
 
 	return &result, nil
diff --git a/yr/yr.go b/yr/yr.go
index 6e049fa..a4f6c86 100644
--- a/yr/yr.go
+++ b/yr/yr.go
@@ -165,7 +165,7 @@ func (c *Client) ForecastCoords(coords *nominatim.Coordinates, location *string)
 	}
 
 	if location == nil {
-		return nil, fmt.Errorf("Location name is not set")
+		return nil, fmt.Errorf("location name is not set")
 	}
 
 	ts := f.Properties.Timeseries